Squatting... a big question.
I have been both : squatter and squatted.
I was squatter when I was "young" in SL. But I would say "ethic squatter". Why ? Because I was living on land which really seemed abandonned. Bought in 2007 or 2008, with very old stuff on it, some "stranger" stuff not removed by owner... I never squatted "living" places. Such squatting doesn't really hurts anyone and gives to SL a little freedom taste, even I know SL is only business, not different than RL. Gently playing with rules is exciting when it doesn't hurt anyone.
I was squatted too in the Linden home I aquired later. People came inside the house and rezzed stuff. Sure I was angry. But what ? In RL I don't let my door opened when I'm away. I don't let the keys in the car. It was my fault. SL gives us many means to protect our land. Then I configured the land to make rez impossible and put banlines around.
I hate banlines, especially on coastal waterways, but my Linden home isn't in such a land...
What I wanted to say is that squatting is fun, but it must be done in a "ethical way". Owners can protect their areas, limiting rez to their group. If they don't, they can't complain about squatters.