Perhaps I'm in the minority, but I never veto AAA for AAA trades, as long as there is an even number of players. A veto, in my opinion, is to prevent an obviously one-sided trade. I've occasionally had a pretty good AAA bat, and a few decent AAA pitchers, but never seen one that unfairly swung the balance of power.
I say that if two people want to make a trade, let them, unless it reeks of collusion or someone grossly taking advantage of a newbie's naivete.