Bathrooms shared by dozens of people are seldom bastions of sparkle. Some students take it in stride, as part of the dorm experience. Others barely notice. But a few are so disgusted they move off campus the first chance they get.
In general, the combined effect of multiple users, general anonymity and questionable cleaning schedules makes it tough to keep communal bathrooms clean. Fungi, bacteria and viruses can live on all sorts of surfaces, and they tend not to clean themselves off. They're typically icky but not dangerous; but every now and then, you can actually catch something from the stuff. It's not unheard of to pick up a gastrointestinal virus from a toilet seat, and it's easy to pick up the "athlete's foot" fungus from a bathroom floor [source: Shaw].
Bathrooms at home can get pretty dirty, too; but in the dorms, and especially in the traditional bathroom-per-floor setup, you can face an added variable: When you don't have the all the amenities of home at your fingertips, bathrooms can start to serve some unintended purposes. They may be dishwashing stations or smoking lounges, which might explain the ash in the shower or the rice clogging up the sink.
Plus, dorm life throws together all sorts of personalities. Some people crave clean, while others don't care a whit. Some might actually care but think someone else will deal with it (where's Mom?) Still, this is your bathroom, too -- the one you visit several times a day, every day, for about a year, and if you like things clean, or at least presentable you might be in for a rude awakening.
So, what to do? First, get some shower shoes, because athlete's foot ain't fun. Then, assess your own unique situation.