It does explain something. ;)
Anyway, there’s basically four possibilities I can think of to explain what’s happening. 1) The guy is, like people suggest, someone to get away from, because he says this to everyone just to get in their pants. 2) The guy is someone fairly inexprienced who is really excited of having found someone they like and being overeager. 3) The guy is looking for a girlfriend to love him, because he is desperate for love, and the “I love you” actually means “I want you to love me”. 4) The guy and the girl have known each other as friends for a long time, and he’s been in love with her for ever and ever, and now just can’t hold it back any longer.
If your friend is freaked out, he should probably tell the guy she is freaked out and to take it a bit slowlier. If she otherwise likes him and it is not probably 1), then if he is able to take her into account and back off a bit, there’s no reason they could not continue dating. If he however isn’t, then it’s probably not going to work out in the long term.