I've adopted a sort of honor-driven set of conditions with the people I've given them to - a "domain traders' code," if you will:

1) If you don't use the domain, I get first refusal to have it back. 2) If you do use the domain, and if I request, you'll give me a link on the site someplace. (More a speculative thing than anything..) 3) If you go on to sell the domain/site for big bucks, you'll remember me and get me something from my Amazon wishlist ;-)

It's all honor-bound and ridiculously hard to enforce, but I'm a big believer in honor, so who knows.. :)