Let me play the "Devil's Advocate" here without wanting to ruffle any feathers or stomp on any egos.

There is nothing wrong with collaboration as long as it is truly a "team effort." Leave your ego at the door if you plan to do many collabs. Be willing to hear your co-writer's ideas thoroughly before commenting or just slamming the door.

Here are the negatives to collaborations:

1. It can often lead to a mediocre song. (Too many cooks in the kitchen can spoil the brew)

2. Many collaborators are not skilled in the art of negotiation and "wear their feelings on their sleeves."

3. Sometimes, the "musicator" assumes that he/she is the senior partner and only "tolerates" the lyricist.

There must be a dozen more reasons but these three seem to be prevalent. Collaboration, as Marc has said, is truly a path to success in the music world of today. I've had several very good collabs and a few complete disasters. Choose your partners carefully, establish ground rules and agreements, expect timeliness and apply the same rules to yourself. Most of all, try to create an atmosphere of levity and enjoy the human aspect of building something together. Best wishes for success.