It really depends on the circumstances. Some companies/industries don't negotiate. Others will, but it really depends on the company and the person getting the job offer.
In my DH's case, he asked for and received 3 weeks of vacation from the start, at both of his last two jobs (current one, and the one he took in 2008). He's also north of 50, with 30 years experience in the nuclear field, so he brings a lot to the table. OTOH, he didn't ask for more money (he was already getting a nice bump), and he got a really good relocation package--better than some of his co-workers did. He even got a raise and large bonus this year, which we weren't expecting, since he hadn't been with the company for a year at the time. But, that speaks to his skills and work ethic--we knew once they got to know him, the money would come, so he didn't want to ask for too much up-front. The vacation time was more important to us.
Through the years, we've never, ever had problems with a company allowing unpaid vacation time for a planned vacation, soon after employment. (Does that make sense? When you're starting in April but have a June vacation all set up, for example). Even companies that won't negotiate other terms have allowed this (I'm looking at you, GE!). In some cases, they'll pay you when you reach 6 months or a year, depending, and sometimes you just take it and don't get paid. Keep in mind, though, that I'm talking about white-collar jobs--I have no idea what might happen if you worked in a bank or machine shop or whatever.