Always put a date in a signed message.
Else, I can just copy/paste the message and signature, and reuse it in 6 months.
EDIT :
Hi can i get a 1 BTC loan please? Pay back Friday when I get my 10 BTC from Coinbase. This is my BTC address. 1G8jPwsohfoQLSwWvvDzR3j1wmwpgiUHYX
Oh, and do not lend to Joseph, he's a known scammer trying desperatly to get some coins to play poker.