I have tried it and I must admit its quite hard. A lot of it comes down to self confidence, which is something I lack at times. I tried to start a '100 strangers' project (check out flickr, there is a group for it) and failed after 3 or so.
If I give it another try, I'll probably use events and functions to try at.
Actually, using the 100 strangers project is a good idea. Tell your subjects exactly why you are taking there photos. Maybe even provide a link to the pictures for them to look at, if you put them online (but warn them that since they are film, it will be a bit longer till they are online!).