Phil Haack blogged about how, as a new Microsoft employee, he's drinking through the firehose [FYI to Phil: Brian Goldfarb has been using this as the motto on his blog since 2003, before Dare's post] and I'd thought I'd add my two cents to the lifecycle of new employees.
Microsoft absolutely has a "sink-or-swim" mentality for new hires (college or professional hires). That doesn't mean there isn't a vast support network or mentoring options, but it does mean that, in general you are given a goal or metric and you can decide how to reach that goal/metric. Unlike other companies where you're told what to do, a good number of jobs at Microsoft, it's up to you to own the goal or the problem.
Ownership can be a double-edged sword, but it seems to be the most effective way to address issues. Ownership, to me, means that you or your team is personally responsible to fix something or meet a goal. This can be a double-edged sword in that other teams that don't "own" something often-times won't put resources towards something you depend on, hence the challenge with cross-group collaboration. In general, I think ownership is the way things get done around Microsoft and the times I've seen shared ownership work is when all teams involved have committed to the goal or fixing the problem.
New Employee Stages
The cycle repeats itself as you get promoted (to a new level of incompetence), switch teams, or switch disciplines (ex: PM to marketing).
To those that are new to Microsoft that are reading this