Where I used to work actually had lots of problems with this. I vaguely recall it coming to a head a while after the iPhone 3G came out and/or about the time various staff members got macs, but I could be wrong. Anyway, it sprang immediately to mind when reading this thread.
It doesn't sound like it would be a big deal, but Windows (and Mac OS X, I've since discovered, mid-7 minute `svn commit'...) just drop the connection if there's an IP conflict. That's actually quite annoying, at the very least. You have to resubmit commits, restart getting latests, your FTP craps out halfway through, file copies go wrong, you lose your remote desktop connection, the code finishes compiling before your web page loads, etc. With any luck, you won't lose any work.
If you don't run your code on the same computer you write it on, you might be less lucky. The debugger craps out and you lose your place, or the file server goes wrong and your code gets an error and stops or whatever while you were in the middle of waiting for it to get somewhere specific. And if you use any home-written tools, they're probably going to be even less resistant to network failures of this nature than the stuff you paid for - which doesn't do a fantastic job in the first place. It all adds up.
Fortunately for me, I wasn't using Remote Desktop all that much, and the device I was working with attached via USB. And I didn't lose any work when the source control just stopped mid-operation. And I could just put headphones on, and block out my colleagues' cries of pain. So maybe that's OK then, and it's no big deal?
I'd like to be able to say what the eventual solution to the problem was, but I don't remember.