As a college freshman, I got totally screwed on a collaborative writing assignment. It's a long story that involves a very sunburned, very cute boy with a very preppy name. While I was shocked and royally pissed off, he ended up dropping out of college, so there.
As a teacher, I like collaborative writing in some instances. On the less-work-for-7-letter-deborah front, fewer papers to grade, group work during class time, all that good stuff. On the it-really-does-have-pedagogical-value front, it's reflective of real-world writing, it fosters community, it can be stimulating, and it exposes students to a variety of different writers with different strengths and skills.
I only craft collaborative assignments in classes with real-world components (Technical Writing and Business Writing). Oh, and I will absolutely create a slacker group.
As a real-world writer, I'm currently getting totally screwed on a collaborative writing assignment, half of a 90-minute presentation with a guy who doesn't return phone calls. We're both rock stars, and someone, somewhere, thought we would be a natural fit. Here's a hint, conference organizers: rock stars do not generally work well together. If they did, they'd be a rock band, not a rock star. It's like asking two divas to sing a duet. Bad.idea.
Nothing more to say really, just crabbing.