I've lived in my house for 30 years and never remember the trees falling down like they have over the past few years. Its very scary, but your best bet is to always use a tree guy with their own insurance. I never checked whether they had worker's comp and why would that ever be my responsiblity? I'm not their employer, the company I hired is.

Tipping? I would never hire a company that asked for that when it comes to tree work. They have a lot of nerve because they charge so much money to begin with.