This doesn't mean the Guidelines are foolproof and always consistently applied.

If you're just trying to read the Guidelines as legalese then it seems to me like there's some serious ambiguity with what exactly the "Reader" section allows.

It seems like Basecamp gets a pass based on the "access to professional databases" exemption. But at what point does a service that caters to consumers AND businesses cross over that line?

The App Store Review Guidelines have been a nightmare to parse through and the Review process an inconsistent mess for many years now. IAP really took it to a whole new level.