From a usage point of view, I don't see the reasoning behind splitting common tools between a business and a consumer product. My email client processes emails regardless if they are private or business-related. I can use my mobile and landline phones for both private and business calls. Why split an online communication tool into two products, except if your plan is to use the consumer product as freemium bait and charge the businesses a premium price?

Lammert, the freemium approach is definitely part of it.

Some professional tools, though, have issues that would simply bog private tools down... things like levels of permission, stricter password access, more fine tuning... and actually less automation and more manual control.

As with professional cameras, to use an analogy... one of the many virtues of pro versions is that they have manual settings... they're not automated. Harder for some people to use, but in consumer models, a professional is always fighting automation, which many non-pros like.

Pricing also a factor, in that it's often cheaper to automate something for an average setting than to include manual control.