I feel both ways on this one.
Yes, the lottery is a tax upon innumeracy, and disproportionally hits the folks who can least afford it. (And yes, as da_Bird points out, it's actually a significantly bad bet compared to most other legal gambling -- qualified because part of the problem with illegal is that you often have no clue what the actual odds are.)
On the other hand... To some extent, this is a perfect illustration of the way I wish we'd treat recreational drugs: legalize, control quality, tax, use the taxes (and the profit, if it's government-supplied) to address social ills, preferably those caused by or causing the problematic behavior. (Which targeting the lottery income to education actually does -- or would if the states didn't reduce funding from other sources to compensate.) The alternative of having people play illegal numbers games run by organized crime would certainly not be an improvement!
I've also spoken to someone who was buying a lottery ticket every week even though he really couldn't afford it. As he explained it, he knew darned well what the odds were and that all he was buying was a bit of fantasy... but he needed that fantasy to help him believe that he was eventually going to get his life turned around. Personally I consider that equivalent to a drug dependency, though it isn't the classic gambling addiction... but I can understand where he was coming from.