thanks everyone for your comments. JimmyL, you make some very valid points and this is a route I'm taking hesitantly. I should have made it clear in my original

thanks everyone for your comments. JimmyL, you make some very valid points and this is a route I'm taking hesitantly. I should have made it clear in my original post why I need to restrict signups in this way. I'm making a trading platform for users to buy & sell collectible items from a certain niche. Without limiting new accounts, there's little to stop someone creating multiple accounts and engaging in fake transactions in order to bump up their feedback, especially during the beta because I won't be charging any fees.