End user license agreements (EULA's) are often in the form of those click-wrap agreements that you agree to when you install software, or subscribe to a service. They are generally enforceable unless they contain unrealistic terms - such as the old Dilbert cartoon where a license required the user to become a towel boy in Bill Gates' mansion.
Most people don't read them. Vendors have been known to put things in them such as an admission that it will install spyware.
They are often chastised for being too long and too hard to read. (I like to think that the ones I draft are short and simple - but then I'm biased.)
Techdirt has a post on the subject that refers to software that purports to analyze a EULA to bring nasty parts to your attention. I tried it on one I drafted recently - and the software liked it. While it might be a useful tool to alert one to relevant keywords, it is no substitute for actually reading it.