This is the exact topic I was going to post about. I've already started a reviews section on my site, and it does get a little traffic, but nobody seems to want to register and write a review. They just want to see what everyone else has said about the product.
I thought about making it so visitors have to log in to even see the reviews, but then search engines wouldn't be able to index the content. Also, my review section is independent, unlike a lot of new review sites that import feeds for reviews from larger well established review sites, so getting started is a bit of a pain.
I'm Leary about doing a contest to get people to review because I had just read something about search engines penalizing sites for doing this, and other related tactics. Even mentioning a certain phrase or abbreviation got one webmaster removed from the G's index. I know that sounds far fetched, but it was confirmed by Matt Cutts. I'd post a link, but I'm new here and not sure if I can do that. Try searching "bit** slapped by google".
One thing I know is people generally won't post anywhere for any reason unless there is something in it for them. So how to we make it of some value to the visitor to write a review?
[edited by: eelixduppy at 4:27 pm (utc) on Jan. 5, 2009]
[edit reason] added link [/edit]