checking identity of people signing up to open a store

Hi there
I was wondering if anyone had any ideas of methods to check the identity of someone opening a store on my marketpress site. Other multi user ecommerce sites always seem to make an identity check for people selling. (etsy, folksy etc) and some dont seem to bother (dawanda etc)

Methods ive seen on similar sites when I open a store...

I am asked for my papal email (as for marketpress) and then a small deposit is made into my account to check the paypal account exists. (I think ebay did this?)

or I am asked for bank details to make a deposit (like etsy, but not feasable to set up for my site)

or I am just asked for a credit card number (again too complicated to set up on a small site)

So the first method seems the easiest and can be done manually

I thinks my reasoning is I dont want people opening a store, and then filling it with spam adverts and other irrelevant or offensive rubbish, or opening a store as a test with non existant products etc. I know the identity check wont necessarily stop this but it would allow me to identify the shop owner incase of problems and confirm that their paypal address is genuine.

Does any one else bother with anything like this? Or should I be less paranoid and just check the sites every so often.