“Hidden in the code of the “Stocks” and “Weather” widgets is a string that sends the IMEI of your phone to a specialized URL that Apple collects.”
“This let[s] Apple know which app you are using when connecting with your iPhone. Obviously, they know the IP address you were using, the stocks companies you are interested [in], and so they can track down their customers all around the world. This also proves that there are probably other apps that do the same. Weather.app is also acting the same way.”
Of course, from a corporate perspective it is good to know a lot about your customers, but this seems to be a big no-no.