In reply to mistrelo:
Depends on the glacier really. Some are very stable - much more than the surrounding terrain - and often they are quite 'unglacier' like when you are on them, covered in rock. The rate at which they move and buckle can be related to their gradient and course (they act like rivers in some ways) so have areas of turbulence and areas that are more still. Season-long camps for peaks like K2 are quite stable, on compression ridges away from the edges that seem to get more distortion.
Always good to spend time on Google earth looking at them, especially the huge ones in the Karakorum where several glaciers merge and the mix of rock makes it easy to see how they are acting.
re actual camping on them; for long stays it's important to build up around your tent site to reduce the effects of sun, so rock walls that provide shadows and platforms that stop direct melting around the edges of your tent. Places like the Baltoro can have days above 30c, and UV degrades ice, so over a season a tent that was flush with the ground when you showed up can be knee height above the surrounding ice when you leave (the tent itself insulating the ice under it from melting).