So I saw this article referenced on Eschaton this morning and went to read it. Kevin Drum said in his article
"Union power in the private sector began to wane in the 1970s, and it's not a coincidence that this was exactly the same time that middle class wages began to stagnate, CEO pay began to skyrocket, and income inequality began increasing inexorably."
I haven't seen a stagnation of middle class wages, but that's only my perception. More importantly, I find the comment to be troubling because Kevin Drum doesn't provide any information to back up his claim. I'd like to see some economic data that backs up that assertion.
What I will say is that based on what I've been reading in Henry Hazlitt's "Economics In One Lesson" unions do little to impact the real wages of their employees, and often reduce the real purchasing power of many people across the economy and drives the prices of goods up.
I can summarize Hazlitt's arguments if anyone's interested, but I'd recommend you pick up his book instead, since he did a fine job writing it.

In my opinion...as harsh as this may sound...I think that unions do nothing more than protect the lazy.