Shouldn't the privilege-gained alert message include the name of the privilege in it? It reads a bit strangely as it is.
E.g. "Congrats, you've gained the privilege — vote up and 8 other privileges" (or something similar).
This would be something like the alert messages in this question.
I got this after clicking through from a sidebar ad on SO to a site I had visited (I think) once before.
(It turns out it was "create chat rooms" and it now looks like this: