Yes, great start! I like the questions. What about:
Do These 13 Common Mistakes Make Your Facebook Contest a Miserable Failure?
or:
Do These 13 Silly Mistakes Make Your Facebook Contest a Miserable Failure?
By using a word like silly or common before mistake, you hint at the idea that these ideas are made by more people than you might think – making the reader slightly more scared that perhaps they’re making these mistakes, too.
Enchant readers. Woo customers. Win business.