IMDB.com(Internet movie database) did that awhile back to me. I had to give them my cell phone or a credit card number(no shit). i figured since they are owned by amazon and Amazon has like 3 of my CC #s already I'd just go ahead and give them my CC #. They put a $1 hold that dropped off in 3 days..For me it was better than giving out my cell to 'em.

Weird shit though that a movie forum wanted that kind of verification..