My wife was sued by the very large company she worked for under a non-compete after she went to a company that they saw as a competitor. They sued her in Texas (even though she worked for them in a Northeast state) and the two companies spent $500K battling it out before it even made it to discovery. We were out $20K personally just in legal fees to have an independent lawyer advising us. Neither company cared about her particularly, but were really fighting each other. When the old employer successfully got an injunction against her, then moved the case to Federal court, and laid out what the first year of the case was going to look like (while she was unable to work at all because of the injunction), she pulled the plug and settled with her old company with an incredibly one sided agreement, basically hamstringing her from working in the industry for the next 18 months.
So, yes, they are sometimes enforced.
