Hosting a Contest on a Website??

[TreeCactus]

Have any of you ever hosted a contest on your website? I wanted to drum things up and get people excited about making up their own designs, so I contacted a couple of needle work shops and asked them if they would sponsor a contest by donating gift certificates - and they did! The purpose of my site is to promote embroidery, especially among my age people who always say things like "wow - can you show me how to do that?" or "I'm just not talented - I couldn't do that" when they sure could do it.

Anyway, in proposing a contest, what are the drawbacks to people joining it? Do people trust each other enough to join in something like that for the fun of it? Or do they automatically think "I'm not going to share my design, someone will steal it" or "How do I know she really has a prize, maybe she's just making that up" or stuff like that?  Am I working against common sense, if I think people would be excited about this kind of thing?

And then, are my rules reasonable???!

Here's the contest: http://www.needlenthread.com/2006/11/embroidery-design-contest-with-prizes.html

Any advice you can give me would be really appreciated!