All online polls are crap.
For starters, it's taken from the universe of MSNBC readers.
As far as "stuffing" such polls, most of the time it can be accomplished quite easily by pulling a cookie out of your files. I was able to take this one three times. The last time, I didn't even bother with the cookie, and it still worked.
We could also go into the "loaded and misleading question" zone if we wanted to. Most fall into that category, some grotesquely so.
Does anyone ever wonder about the regular polls, and that they exclude everyone in the Universe Of Those Who Tell Phone Pollsters To Bugger Off?