When crossing a glacier (or other mountaineering activity for that matter) I've heard that roping everyone together without having a fixed anchor is falling out of fashion since more often than not if someone takes a tumble into a crevasse then end up pulling their partner(s) in with them. What is the current expert advice? Is it better to tie everyone together, or keep the rope handily unattached and ready to perform a rescue if someone goes in?
If you have some credible people saying not to be roped up, I'd love to see it, because that sounds completely insane to me. Here's why:
If you are traveling on a glacier without being roped up, there is a very, very, very good chance that you will die if you fall in a crevasse. This isn't because you vanish into nowhere, but because you will get what we morbidly call "corked" - you will get squished between the two sides and get stuck, most likely sustaining massive injuries on the way. To compound the issue, a rescue in this case can be nearly impossible to an average group for several reasons. First, access to a person's harness or other attachment points will be limited. Second, if you are so far down as to be stuck, rope length becomes a serious potential issue. Third, close contact with ice for a long period is a major hypothermia risk.
Good training, practice, and technique makes the risk of dragging in partners very low, and the potential gain of being able to rescue someone very high. Keeping a good number of people on a team is also helpful (two people is an obvious minimum, but three or four is better if you have them). I suppose I can imagine situations where a very poorly prepared group wouldn't rope up, but that should be avoided from the very beginning.
This isn't to say that it doesn't happen. A very good friend of mine, Jim Davidson, recently wrote a book about his experience on Rainier, where he fell into a crevasse, dragging his partner with him. His partner and dear friend, Mike Price, died in the accident, and Jim managed to climb his way out by the skin of his teeth (the book is called The Ledge).
So what this boils down to is that yes, as a rope team you risk accidents that involve more than just the first person to fall. Those risks can be minimized and managed carefully, but they never go away entirely. Training, experience, practice, and good equipment are all necessary to avoid those situations.