This has been bothering me since I upgraded to iTunes 7, and I finally laid hands on a copy of v6 to confirm: in v7, Apple seems to be pushing the new MiniStore they introduced in v6.0.2, as in: they don't make turning it off nearly as obvious anymore. Maybe they didn't like the fact that they were subsequently forced into asking permission to run the store, because in v7, there is no 'click down here to toggle me on/off' button. iTunes 7 is pictured above, while a shot of v6's button is below.
Yes, users can toggle this store under the View menu in iTunes 7, but the point is they removed the instructional piece, as well as any obvious, visible UI for toggling the store. A missing button might not be a big deal to the typical iTunes-familiar user, but there are plenty others out there who don't bother to go hunting for things like this when they get moved (remember what happened when Microsoft re-arranged the Start menu for Windows XP? Riots, mass panic and a severe shortage of duct tape), and they relegate themselves to complaining about how [insert explicative and optional insult] Apple is for doing this.
C'mon Apple, we know you love your store (and we're pretty keen on it ourselves), but you don't need to pull UI tricks like this on your users. Besides, there's plenty of toolbar space down there for everybody; especially for a button that used to live there to begin with.