I suppose I should just let Mark touch this one, but...

Yes, airplanes routinely land on contaminated runways. The company's ops specs dictate the maximum landing weight based on a bunch of factors, and the contaminated runway is one of them. Therefore, you can get a weight restriction because the maximum landing weight is really low, and the aircraft won't be able to burn enough fuel to be under that threshold. So, ya gotta bump bags/people to insure you're under that weight. The amount of contamination on a runway is pretty much measured by a "braking action" report which is either compiled by the company or ATC for each airport.

Now, if there's one thing that pisses me off, it's passengers who think they know more than the flight crews/dispatch. Folks, these guys are trained professionals. I will concede that they are not perfect and make mistakes. That said, these guys have much much more training and experience than you do, and if they don't think it's safe to go, they won't go. These guys have reputations, FAA ratings, and jobs on the line, and they aren't worth risking to "hot dog" a seriously questionable flight. All you're asking to do in this situation is to "out guess" the pros, and that's all you're going to do, because I doubt that even your educated guess is going to be better than their experience, training, and knowledge.

Sometimes I hear complaints that the unions have work rules that "screw" the passengers. Most of these rules are actually in it for your protection. My company's pilots get paid when a flight cancels, which is a good thing. Why? Some of these guys aren't paid well, or maybe they just have a lot of bills to pay. Getting paid only for completing a trip encourages pilots to fly when they probably shouldn't. Making sure they get paid ensures that pay isn't a primary issue. Second, some of these guys work long hours under certain conditions. Fatigue rules exist so that if the pilots have been flying for three days straight, is at the end of their trip, has some sort of delay, some nav/autopilot stuff in the cockpit is deferred, and there is serious weather enroute, that they're allowed to say, "Screw it. We're tired, and we think that compromises the safety of the flight. We're not going."

Sorry for my rant, it's a pet peeve of mine. I know a lot more about flying airplanes than the general (and even frequent flying) public, and I know a lot more about airline ops than said groups as well. Exactly how much do I know? Enough to know I know nowhere near enough to second guess a crew's choice to fly.