It could be a trap. Mostly, such websites on internet are made just for the purpose of stealing social accounts, like facebook or twitter etc. When you insert your account credentials and press log in, the information is sent directly to the person who has created the fake site. So, everyone should be careful with these things as they don't always give what is said.
I don't say this service is like that, but i'm just saying that most of them are. So, it is just a warning. Do it on your own risk.