Why does an app read my phone's IMEI number? An awful lot of them do What reasons should an app have to need my phone's International Mobile Equipment Identity number?  I noticed that unreasonably many of ordinary apps have the "phone state and identity" permission.  For example, Remember the Milk.  What do they ask it for?  Am I insufficiently paranoid?
Many apps use the IMEI for analytics purposes, for example counting users. Most tools like Google Analytics or Flurry need a unique ID per phone, so the IMEI fits quite well.

Note that this doesn't work on non-cellular platforms (like tablets), and the IMEI can also be faked: this is why some apps choose a different system (see this article).