I've never understood it and never will.
I don't care about booing, it's the most close-to-legit bad comment to give, but shouting whoever evicted "off! off!" and not letting them to finish a sentance is just rude.
You got Adjoa out, she'll be "off" the moment the interview is over - The game is over for both the evictee and the crowd, get over yourself and move on....
Adjoa wasn't THAT bad to deserve this treatment by the crowd (and that comes from someone who wanted her out).
I hate when the crowd is stuck on rent-a-mob mode.