Yes, I helped a friend of mine a couple of years ago in Vancouver. He and his family wanted to purchase an older character home in an established neighborhood where over 50% of older homes where/still are being torn down and new homes are being build (either spec or custom) on the properties. He specifically said in the letter that his family would not tear the house down, and that they loved the house as is and wanted to enjoy the existing home and great area with his family - it was was the deal clincher he later found out, as the previous owners had lived in the same home for 50 years and had a real emotional attachment to the property. In fact builders had offered more $, but in the end, my friend's letter "won the day".

@Gord, any chance you have a copy of the letter that you could share?

Matthew, do you have an agent helping you with the purchase? I'd seriously consider letting them handle the door-to-door. @GraceHomes has printed flyers with a picture of our clients (with their permission of course) and dropped flyers and followed up with door-to-door before. It works wonders.

If I was your agent, or even you, I'd be nervous about facing the sellers directly. I love it when buyers come to one of our Open Houses. I get an amazing read on them, their point in life, their motivation for moving, etc. And it's happened numerous times that I've been representing a seller and an offer comes in from someone that came through the open house. I can advise my seller all about these people and we have been able to squeeze more money in negotations because we know they have family/friends on the street or they really want that school district, etc. If they had done a showing with their Realtor and I never got to meet them, it would be a more blind negotation and we wouldn't of had that upper hand.

Use your agent as your shield.

If it was me, or if I was doing this on behalf of a client, I would go with an approach that was slightly more casual and a bit less direct (unless you have one specific house you really want).
Instead of door knocking, I'd spend some time in the area and talk to people when they're walking around (dog parks and playgrounds can be a great source to scope out information on a neighbourhood). Approach it with a casual attitude, express your love for "their" community and see if they give you any leads that you can then directly target. You don’t walk to be the “creepy guy stalking the playground”, but if you show a genuine interest in learning more about a community, people may be more receptive.
I'd also try talking to mail carriers and workers / owners in local establishments (more so anything that is family run like a diner or great breakfast spot vs. Starbucks) to see if they’ve heard any chatter about someone thinking of moving. This can also give you a great understanding of what it will be like to live in the area.
It’s been my experience that people don’t want to be solicited when they’re in the comfort of their own home. I have had much more success in taking a less direct approach, although it can take more of your time. You may get a different reaction then I would, because I’m a Realtor - people tend to put up their guard when they think you’re trying to sell them something.
As for mail outs, or leaving a letter in their mailbox, unless it’s specifically targeting the house, they may not take a generic flyer / letter too seriously.

Hey @Matt,
I've done this before with flyers for a client who desperately wanted to get into a neighbourhood. I wrote a nice long letter explaining the situation. I didn't get any bites so I went back out and door knocked every house. People were surprisingly friendly. I got an exclusive listing/sale that way.
Just as advice though, as a buyer you don't want to be the one going door to door in my opinion. It will hurt your negotiating power if the sellers know your desperate enough to knock on their doors to see if they want to sell. I'd let the agent do the door knocking as well. Just my 2 cents. Good Luck!

Hey everyone,
Thanks for the input! I think I am going to try doing door-to-door with my wife. Of course our Realtor offered, but I think there is something nice about doing it our selves.
I am going to be crafting the letter this week.
Here are the key points that I want to hit:
- We are a young couple, going to be raising a family soon
- Have walked by their house many times, and liked the charm and character of their house
- We both grew up around the corner, and we want to live in a family orientated neighbourhood
- If they have any interest in selling, we would like to see the insite and discuss the possibility of buying it.
- Extremely serious
- If they are not interested, but know someone that might be, please let us know.
Am I missing anything?

Good plan Mathew. It worked for my neighbour below me. He lost on the bidding war for my place (lost to me I might add!). He went on to put a little sticky note on the mailboxes of the same units on lower floors and one guy called him back. He later bought the place for a bit less than I paid for mine and did the deal privately. Unfortunately his realtor lost out on a commission but hey, that's this business we're in. You win some you lose some but at the end of the day it's all about finding the perfect home. Do what you've gotta do.
Just my two cents re: note. I wouldn't add too much detail. If you get to sappy and go in to too much detail it may come across as one of those Nigerian scam letters and not taken seriously. I'd keep it short and sweet. I would include your phone number, email address and a brief note about how you specifically like their place. Hand written would be helpful.
Best of luck.

not on the buying side but my ex-neighbour SOLD her house in 1 day by handing out flyers in her neighbourhood (She went with 3 young children of hers, I guess this makes people stop and pay attention to her) . she did not spend a dime in agent fees. It's wild and my jaw dropped to the floor when I heard this.
http://www.home2price.com

Just as an update, I purchased a house on an awesome street in the neighbourhood that I was looking in through the door-to-door lettering.
The sellers are super nice, and we all were really happy with the deal.

@"Matthew Slutsky" have you got a copy of the letter that you used?

Sorry @Shragi Aron, I don't have it anymore.