People are entitled to Boo if they don't think the level of performance on the pitch Is at an acceptable level. It's not something I would do myself because it's counter productive, I'd much rather try and encourage the team rather than depress them but each to their own.
We as Evertonian's should be expecting more from the lads on the pitch and I think that's what gets people frustrated and the booing comes out. We are no longer the plucky underdogs of the Moyes era but rather a team with a 30m pound striker leading the line. At the moment the players on the pitch, Martinez himself and most of all the men on the board all need to be doing better.
I guess we shall see what develops over the next few days/weeks.