Its a little different because I'm at a dot commer, and we all use AIM for day to day communication. Also, not every one here is a crazy technical guru, but most people are adept users, so we don't have to deal with the old/young computer literacy barrier that a lot of other companies do.
I have no problem picking up the phone, however I do avoid it for one reason. I have every email I've ever sent, and I log each and every one of my IMs. I think it bumps up credibility, and if anyone ever says "I didn't receive that" I can open the log, look up the date and cover my ass. That's a lot harder to do with a phone conversation.
Also, IM is more or less in real time, and you can have a back and forth conversation with several people at one time, which is important for me as a platform manager because I'm constantly relaying information between users and a couple of support teams.
The only advantage I see to using the phone is when I need to talk to someone right now AND I need to grab 100% of their attention for something that's very time sensitive.
Now: 07 Porsche Cayman S | 18 VW Tiguan
Then: 18 VW GTI Autobahn | 95 BMW M3 | 15 VW GTI SE | 12 Kia Optima SX | 2009 VW GTI | 00 BMW 540i Sport | 90 Mazda Miata | 94 Yamaha FZR600R | 1993 Suzuki GS500E | 2003 BMW 325i | 95 Saab 900S