I've been asked about trees many times over the years. Here's a great article regarding tree laws in Mass.

http://www.linkedin.com/news?viewArticle=&articleID=736615091&gid=1853086&type=member&item=68457194&articleURL=http%3A%2F%2Fwww%2Emassrealestatelawblog%2Ecom%2F2011%2F08%2F29%2Firene-mailbag-who-is-responsible-if-my-neighbors-tree-fell-on-my-house-car-shed-or-swingset%2F&urlhash=45SX&goback=%2Egde_1853086_member_68457194