According to Bruce Schneier, Blizzard Entertainment uses spyware to check compliance with their EULA - and it's one that looks at much more than just the data from their own program, but also additional data from other applications ...
Concerning because it doesn't just read the data from its own program - but even then it would still be concerning if it were limited to Blizzard Entertainment's software. Or did any of the users of the software agree to this monitoring? To the loading of code onto their own computer? To searching system lists for information? To sending this information over the Internet?
It is also questionable how such practices can be in compliance with data protection regulations, for example in Germany.