Mac not tonight

Can someone put V-Mars on the case as to where Mac has disappeared to? (I know they've technically explained her absence most episodes, but come on). It must be sort of a kick in the pants to be made a regular character on a show and then be on considerably less than you were before. The whole revolving cast thing is understandable due to budget concerns, but at least last season it was dealt with in a way that...made sense (Duncan fleeing to Australia, Wallace going off with his real dad). The way it's played out so far in season 3 is like if there were some "Friends" episodes with only Joey, Chandler and Monica, and some with Joey, Chandler, Monica and Ross, and some with Joey, Chandler and Ross, a few with Joey, Chandler and Phoebe, and maybe one even with Joey, Phoebe and Rachel, but never one with, you know. All six of those annoying people.