I think the key here is "without taking advantage of other opportunities". If you're unemployed for a couple years and you don't do anything, then you're signaling something very important to an employer: passivity. A fresh grad with no experience has no experience, but there's also no information to indicate that they won't be a good employee. A two-year unemployed worker has no experience and has two years worth of unsuccessful choices. Which would you hire?

The way to beat that cycle is to do something - other than looking for jobs - with that time. I've got gaps of 4 months and 6 months on my resume (actually more like a year and a half if you count a "startup" as unemployment, but I don't), and it's never been a problem - because I was finishing up the rewrite of a 100,000 user website with the first gap, and open-sourcing the remnants of my startup with the second. I've got friends with 2-3 years of funemployment on their resumes, but they did things like starting a non-profit in Vietnam or Peace Corps work in Peru, and ended up at the very tops of their fields. Unemployment by itself doesn't result in poor career prospects, but not going after what you want and seizing the opportunities that are available to you does.