People don't think about it, as they surf the web, or hand over a bar coded keyring card when checking out in stores to get discounts. The amount of information being collected about a person just from keeping track of what they buy is frightening to consider. Merchants - online and offline - presumably use this information to better serve customers, serving them with ads and coupons that are actually useful to them. But, merchants aren't the only ones paying attention anymore.
Hospitals are starting to get into the business of demographic research, presumably for the purpose of helping patients live healthier lives. This may seem like a noble cause, however it does have a creepy side as well. People are accustomed to keeping a certain level of privacy in their lives, and this certainly is crossing a line that has existed for a very long time.
Government and insurance companies are encouraging this move, primarily by charging fines when people return to medical facilities for additional care too soon. If healthcare providers can track purchases like fatty foods, alcohol, and tobacco, they can begin to calculate the likelihood that a person will end up in the hospital for heart or respiratory problems. Additionally, they could find out whether or not patients are actually purchasing prescribed medications.
As for UPMC, they are collecting demographic information on patients, but haven't gone to the point of tracking their purchases - yet.
Theoretically, the more information healthcare providers have on their patients, the better they can treat them. But, there has to be a limit somewhere, especially since it would be too easy (and tempting) to misuse personal information to micromanage people's lives through medical fees and fines levied for poor health choices.