Slashdot asked the other day, " Why Are Major Companies Exiting the Spam Filtering Business? " It sounds a bit like they're trying to take two events and define them together as a trend, but I don't think that holds up under scrutiny. I guess they've got a point about MXLogic. MxLogic was purchased by McAfee in 2009. McAfee was bought up by Intel in 2010. And now Inte…