Of course there are all kinds of crazy scenarios. I'm sure there are institutions out there with legitimate needs for an uncapped mailbox. However the "Google approach" is totally unrealistic in a business environment and I suspect that you're either desktop support or a user (I don't mean this in a jerkoff way, it's just a very "other side" sort of opinion)
Your suspicions would be wrong. I haven't had a helpdesk level title in probably 8 years or so. While I do have to deal with helpdesk level calls more often than I'd like because I'm in the office a lot, I'm an engineer with a semi-small (~30 users) IT company that's main focus is on voice and infrastructure. I prefer to stay away from Windows as much as possible but I still end up getting drug into those projects too.
I just checked and our Exchange backups took ~3.75hrs and were ~112G last night.
Most companies function in some sort of "project" environment. A user works on a "project" and when the project is complete it is archived. That archived pst should be put in a network share with the rest of the project crap which is write protected after the job is complete. In your scenario, how do you get all of the emails for a project? Look up each team member and have them turn around and create a pst, then merge them all into one? You think that's easier than looking up a project folder and loading up the pst for whatever you need?
Anything relevant to a project should be attached to that project in our system. Emails aren't handled in any special fashion.
I'll have to spend some more time on this tonight.. I seriously cannot think of any business entity that would have a need for complete access to -all- email for -all- time. Eventually that mailbox will need sorted through, and it will be a HUGE pita to sort out 5-10gb worth of mail without losing track of anything.
I know most/all of the reasons for mailbox quotas. Keeping backups running within their alloted time-frames, Exchange database size limits, disk space in general, Exchange sucks in general, etc.
But I'm a pack rat so I'm looking at it from the opposite perspective, i.e. why should I have to worry about deleting email when it's the server's job to maintain that for me? The server is here to help me, not vice versa. And while I think unlimited should be possible, I know that doesn't really jive with reality. But some of the people here posting mailbox quotas of 150M are just insane. I'd be extremely pissed if I was given under 1G.