In the early version of SC2 (when Rax was able to be built before supply) EARLY reaper rushes were very effective. Recently, as far as I read few times on gaming.se and teamliquid, reaper rushes are not used too often. I never even played against it on ladder (until yesterday).
I was playing yesterday against a reaper rush for the first time, and my opponent killed around 10-12 of my SCVs. (I did few stupid misselections: didn't pull SCVs back to defense, didn't get my marines to kill reapers in time.)
In the next game after that I tried to do it myself. With 3 reapers, I killed 7 or 9 of my opponent's SCVs.
Not every map is good for reaper harass, but if used smartly, it could be a real benefit.
My Question: Why this strategy is not used so often? Are there any drawbacks that I don't see?