Having used other sites that were designed for hook-ups (and this site really isn't), it's typical.
Some guys are just curious but afraid to actually go through with it, some are real flakes.

I don't think you are doing anything wrong, but you need to try to more carefully screen out those that show signs of tentativeness. Somewhat anonymous users that try not to disclose anything, first-timers that express doubts, and those that seem very concerned about being discreet are the ones I find tend to disappear without a trace or have endless excuses. Also, those that seem to drag on a conversation forever without any commitment to time or place are the ones that usually don't follow through.

I'm not saying dismiss someone who does those things, but be aware and try to steer the conversation to their intent, see if they are unsure before wasting a lot of time on them. Sooner or later, you'll come across someone like me, who loves to be naked with others!

I don’t I think it’s unusual for this to happen. I myself have backed out once or twice, but always having the courtesy to let the person know. Mostly when I say I’ll meet with somebody I’ll meet with them.

It is good to always meet the first time just to get acquainted. That way, you each can find out if it’s obvious that you’re not a good fit.