The answers I have seen so far reveal (no surpise) a wide variance in what is expected of the Help Desk as well as in staffing it.
I am the Helpdesk Manager at my company, but this has evolved over the past five years and is somewhat misleading. At first, we had a team of administrators who took calls from the 500 employees of the company. Any person taking a call can and should resolve the problem; our "first call resolution rate" was about 100 percent and there was no distinction between helpdesk and I.T.
As to cubicles vs bullpen, it depends. IF the helpdesk team are experienced administrators, then immediate proximity is extremely useful, you can detect network emergencies far more quickly. It is also very good to have a manager, or more experienced tech, in proximity to apprentices.
The downside is well known and obvious -- NOISE. This can be minimized by padded furniture rather than the hardwood cubes we've turned to each other and actually focuses noise across the bullpen.
*IF* the helpdesk is corporate, then the helpdesk needs to be as tightly integrated as possible with I.T. I forward calls pertaining to SQL server problems directly to the SQL programmer for instance.
Also, *IF* your helpdesk is corporate, put REAL TALENT on the helpdesk -- my tier 1 guy is an MCSE and it is not very often we have to escalate.
ROTATE the jobs; don't allow a corporate culture to come into existence of "just" helpdesk. Make it so that Helpdesk is recognized for what it is -- once you've created a cow, just how do you think you are going to keep it contented? Don't let "creating the cow" earn more money and respect than "keeping the cow contented."
It's inevitable; but I counter it, pointing out to the self-important programmers that, hey, I get to talk to HUNDREDS of people, MY name is known, is YOURS?
But like I say, mix it up a bit; let every I.T. worker do a stint on the helpdesk, and conversely, every helpdesk worker is encouraged to program, write SQL queries, make web pages.