Tree activists are against doing it to live trees. It does damage em, and I wouldn't do it to one of mine... maybe a trash tree, away from my house.
I need to learn how to carve like that. Instead of taking em all the way down, I could charge em for me to carve something cool.
Around here they do bears instead of faces. Some of them are pretty neat. I don't have any pics at this time. If I come up with some I'll post, or at least e-mail to MasterBlaster.