Almost my entire (small) company is based in NYC, but we have one programmer in Europe. He just adjusts his schedule to US Eastern Time hours. Might be harder if he was in Australia, but that still leaves a lot of flexibility.
Heck, as I'm writing this, it's 11:20 am where I live, and I just overheard my sister get out of bed in the next room. Last night, she was taking an online MCAT prep course until after I went to bed around midnight. She could easily work in a different timezone.
In my experience, Eastern Time to Central European Time synchronous communications works pretty well without anyone having to deviate too much from normal working hours. Add Pacific Time to the mix and you're starting to need people willing to take calls at 6am and/or in the evening.
But, yes, some people are willing to adjust their personal time zones. I know someone who lives in Hawaii and runs a PR agency with mainland US clients. She just normally gets up very early.
Heck, as I'm writing this, it's 11:20 am where I live, and I just overheard my sister get out of bed in the next room. Last night, she was taking an online MCAT prep course until after I went to bed around midnight. She could easily work in a different timezone.