When not signed in, up-voting a request pops up a nice box prompting for login...link to create account takes you to another nice box to collect needed info...and then it dies:
FF 10.0.2 = nothing happens...at all (my FF is super locked-down so who knows).

Chrome 17.0.963.56 and Safari 5.1.1: spits out a 75% hidden message in the upper left hand corner. Can't read it, but clicking the button (can only read the last letter "k") or not clicking it and refreshing, yields nothing. Clicking on it does trigger some sort of failed event loop as the next time you click on vote up, it throws the message:
Sorry but anonymous users cannot vote.
Please login or create an account here.
and clicking the "here" sends you off to the proper sign-up page.

Ref. screenshot for better description.