OMG -- where do I even start?  If you look at the landscape, the protections for labor were very different 30 years ago than they are now.  That's not because of workers -- it's because of business fighting, challenging, and gutting the regulations.  It's been a tidal wave of court battles -- some big, some small.

In general, full time workers received healthcare, pension, and other benefits, as well as certain protections regarding hiring and firing, and things like sick leave, maternity leave, and vacation time (remember that?).  

There were regulations so businesses couldn't subvert the law by, say, hiring all their employees for 39 hours a week.  There were also rules about who, why, and for how long someone could be hired as a temp or a sub-contractor.  Remember when temps were actually, y'know, temporary workers?  filling in for someone on vacation?  And this doesn't even touch on outsourcing, etc.

Now it's just a free-for-all -- at least down here with the hoi polloi.  It's not just Wal-mart, they're just one of the big guns.  But it's basically been a class war, although if you point it out, people accuse you of instigating a class war.  That's why it's taken so long to notice it if you aren't on the front lines.

If you seriously want to know about this, you have a lot of reading to do.  I suggest you start with the congressional pdf report linked on this page.  Here's a summary (bold is mine):

The report also provides a comprehensive review of Wal-Mart's numerous anti-worker practices, including union-busting activities, discrimination against women and disabled workers, violation of child and undocumented labor laws, unpaid overtime, and unsafe workplace policies, like locking workers into stores overnight. Wal-Mart has been the subject of thousands of lawsuits and critical media scrutiny on all of these issues. The Washington Post just reported on labor abuses in China at the hands of Wal-Mart.

Maybe we can eventually make language a complete impediment to understanding. -Hobbes