One week is far too short a time! It is not as if a reviewer has nothing else to do in his life!
I am already doing it. I never accept to review when I have less than three weeks. However, when I have submitted to these journals that give one week to review, frequently I have been waiting more than one month... and sometimes the MS was directly rejected by the editor (but one month after submission!).
I've had the same and it annoyed me at the time. They then requested I review the returned paper after major revisions in 3 days! I probably won't review for that journal again.