That's an interesting approach, but if the "pro" features are something the user really needs, then don't you risk losing a sub if the feature is withheld until you "get to know each other?"
You could give them 15 days free use, and only charge it after that... there is a risk that the charge doesn't go through (in which case you've given a couple weeks free service - big deal), but otherwise, you've just made it much less useful for card testing (to the point that they certainly won't use your site).
Yeah, that's all of the upside and none of the downside really. Introducing ANY kind of delay between taking the order and charging the card will just about eliminate these kinds of fraudulent transactions.