Is that any different from using, say, Gmail or Google Apps? Not saying that Google is looking at that data but this is a problem with essentially every web-based communication tool. People shouldn't have an expectation of privacy or security just because it's a company they know/like or it's a popular tool.
- location and contact history (cell phones)
- message history and address book (email, social network)
- interests/activities (calendars, event tools, feed
- browsing history
As an engineer, think about the evil fun you could have with that data. You could really mess somebody up if you didn't like them.
None of this is legal, and if discovered there would be a legal case to answer.