This is a good article to which Instapundit linked concerning the very slow pace of re-employment.
In our own office we laid off two secretaries early last year, and have only lately upped the head-count by moving a part-timer to a full-time clerk/receptionist position. In part not rehiring two full-time secretaries arises from a partner leaving. On the other hand, a barely full-time associate has been transitioning to complete full-time as she completes some extra schooling which we funded for her. She will very soon replace the partner in terms of "billable hours" contributed.
Taking up part of the slack has been an increasing use by the "time-keepers" (the lawyers and paralegals) of the advanced software that we have. We simply don't need clerks to finish off a lot of the work - we can do it ourselves because of the technology at hand. We continue to edge up the learning curve with that technology.
Finally, the layoffs we made were of people who were barely performing anyway. In fact, we laid them off not because the recession had bitten into revenues, but because it made us stop and think about the overhead issue. We laid them off because we realized that we could do without them. And we have become less tolerant of average performers, as these two people barely were.
I wouldn't be surprised if in some respects we are a microcosm of what is happening in some areas of the private-sector economy where people are not being hired back.