I like a tasteless joke as much as the next guy...

... but if this was done on purpose, someone at Google needs to be fired.

Go to:
http://images.google.com/images?q=yiddish

Now note the "Also Try:" link.

At this point my theory is either a disgruntled employee or a fight-club style hack.

Okay, maybe that's more of a hope than a theory.

[EDIT: As of today, it looks like someone at Google cleaned things up, so searching for "Yiddish" no longer suggests an Also Try link to "zyklon b"]