Coming from a relatively small company (~150), and being one of a team of 2 in IT, I have frequent interactions with everybody in the company - internal sales teams, staff in our warehouse, external sales reps from all over the country, right up to senior management (including the semi-retired founder of the company who lives out in Spain).
Not only do I get to know people internal to the company, but I also have our hardware providers, software providers, and service providers who I speak to on a semi-regular basis. Not to mention all the people who mysteriously have my direct dial trying to flog me stuff (must have been previous IT folk, as it's not a widely known number and I'm very picky about who I give it out to - for just this reason!).
Your myth is totally wrong, at least from where I am. Our office is all open plan (though we are against a wall for the sensitive issues we deal with), and in my opinion it's much better that way and has a much more social atmosphere. I'd hate to be "locked up" in some office down some corridor where nobody ever goes, and quite frankly I'd probably leave if we were "hidden away" somewhere.
It's myths like this that can give our profession a bad reputation, and if I ever hear anybody (in a serious manner) coming out with ergh, bloody IT, miserable, unsociable gits who are just out to spoil our fun I will do my very best to prove them wrong and that I'm just as nice a person as they are. For those new starters we have that genuinely believe IT are unsociable and non fun loving people, all the new starters in my time have changed that opinion, so I think I'm doing something right!
Unsociable hours are also another part of the myth. Our business is open from 8:00AM to 7:00PM, so I do the same 8.5 hours a day as everybody else does, but we do 2 shifts of 8:00 - 4:30 and 10:30 - 7:00 so there's IT coverage at all times. Sure once in a blue moon I might get a phone call at some ridiculous hour in the morning, but there's always a genuine serious problem, and it really is only once in a blue moon (say once a year if I'm lucky). There's also the odd weekend I'll be at the office, but it's only for maintenance that can't be performed during business hours, and I'll either be on overtime or get time in lieu.
In short: most myths you hear about IT folk are wrong, and don't let anybody else tell you otherwise!