Not so long ago, we simplify registration process at our site leaving only the username field...
As a consequence, we are faced with a problem of creating multiple accounts by the same user and abusing faucet (faucet at our site - 0.007 mBTC and only request every 3 hours when balance is zero).
Guys, what solutions do you recommend?

Thank you!
a classic problem for all people who try to build faucet or any paid site,i think abusing faucet can be perevented with ip configuration,our site must be can detected any ip address and validate it as first user,if detected same ip,block it permanently. and also you can block any user by bitcoin addresses,if you detected multiple bitcoin address.