I generally meant some kind of digestible deliverable within the context of the core product. You need to have a well defined goal that is achievable within the amount of time the person is there, otherwise it will not be a good experience for the intern or the company. So let me correct... most of what is produced by interns is part of the core product and released to production.
As a former Bloomberg intern, you're right – you try very hard to make sure interns are working on real projects that are deliverable over the course of the summer. That said, the projects are often completely isolated from what will have real impact on users on a day to day basis. This isn't a problem, per se, but I've had other internships where the work I was doing over the summer was virtually indistinguishable from that of a new full-time employee. I imagine this was largely because it was a much smaller company with a much smaller product.
I don't mean this as a criticism – Bloomberg tries very hard to make sure interns have a great experience and usually succeeds. But there is a difference and I, personally, preferred the other experience.
It also depends a lot on what team you wind up picking. Just speaking for the interns in our infrastructure team, we try to make them develop things that have an impact. You should let me know what group you were with so I can deliver the anonymous feedback :)
