2. MS rarely sues over patent matters, usually they do cross licensing deals, so maybe they tried that here (as clear from Salesforce jan filing) and that didn't work out. I am sure Salesforce being quite a old player will have patents MS might be interested in using/licensing.
3. People criticizing the patents they are suing for, remember two latest case that MS lost, one of them for basically saving a word file in xml format. They lost millions and The judge actually ordered them to stop shipping Office till they fix it. Based on that as a shareholder I would want them to go out and make some money from their patent arsenal even if it involves suing.