What's Up with StumbleUpon?

I just ran across quite possibly the worst thing I have see all day (admittedly it is only 7 minutes into the day, but...). I clicked thumbs up to stumble a page and was greeted with this:
This single thing will decrease my StumbleUpon discoveries by probably 85%. Filling out a captcha every time I discover a site! I am outraged. I already don't like all the steps it takes to discover a site; this just makes it longer.
UPDATE: This doesn't happen every time, just every time I don't want it to happen.