As we've done with other nascent start-ups, I'm sure we'll all do a pretty bad job at foreseeing how it ultimately gets used, including me, but I want to throw this thought out there because I'm seeing a lot of criticism that's very high-level:

"Discovery" is something all these social sites, at the bare-minimum, do pretty well, and people use. No matter if the social object is music (last.fm), a link (Facebook/Google Reader/Twitter), (books) Goodreads, etc, it's a pretty well-trodden path: surface stuff passively (last.fm) or actively (Goodreads) to help your friends discover.

At the very least, saving money aside, Blippy is showing us what we are likely be interested in (because they are friends or people we otherwise respect + follow) are buying. And we're probably gonna wanna click over and see what it is, even if we don't end up buying/eating/driving/reading it.

To deny Blippy this utility, is to deny all social software of the discovery utility.

Since SO much human activity has commerce underneath it, the potential of Blippy to do all the same stuff the rest of the Internet is good at "How this person fixed their bookcase," "Who that person uses for bike repair," the potential is pretty clear, if a little low-level.

I question not the potential of how sharing consumer activity could be useful, only individual executions of it.