Or is it about those who are still employed and worked to exhaustion and illness because the boss refuses to hire more help?

It's actually a very positive sign. People jump for a number of reasons, but especially at this stage of the recovery, it's very likely that they have a clear job opportunity to jump to, rather than just burning out. When people are fearful about the prospects of getting a new job, they're going to grin and bear it, no matter how bad. However, if the better opportunity is relatively solid, then they will jump. It also means that wages will likely start to go up relatively soon, as employers start bidding up prospective salaries in order to attract key talent. This opens up positions that are vacated that may not be ideal, but they're there, which in turn ultimately means that that part of the labor force that has had trouble finding jobs has more opportunities as well.

There's another major factor. The economy collapsed in late 2008. It's now 2012. The first Boomers were born in 1943, which means that they are now 69. The Baby Boomer birth rate peaked nine years later, in 1952, which means that there is a demographic peak that is turning 60 this year. Their employability is an increasingly major problem as the positions that are opening are increasingly STEM or medical related, while this generation is overwhelmingly employed in services or the FIRE sector. Not surprisingly, this particular group is disproportionately white, male, and conservative, or the bulwark of the Tea Party. For them, the recession will likely continue for the rest of their "working" lives.