You would think that they would have thought of this maybe in 2006 when people were making money at blogging:

According to Andrea Mannino of the Philadelphia Department of Revenue, in fact, simply choosing the option to make money from ads — regardless of how much or little money is actually generated — qualifies a blog as a business. The same rules apply to freelance writers. As former City Paper news editor Doron Taussig once lamented [Slant, "Taxed Out," April 28, 2005], the city considers freelancers — which both Bess and Barry are, in addition to their blog work — "businesses," and requires them to pay for a license and pay taxes on their profits, on top of their state and federal taxes. Mannino says the city doesn't keep track of how many bloggers and small-website owners are affected.

It can see lumping freelance writers and bloggers together as a business class if they are actually making above a certain level of income, say $5,000 a year. But to license someone just to have a hobby is a bit weird. I would expect well under 1% of all bloggers actually make reportable net income from tapping away at the keys. Does it matter that this might deter people from blogging? And does it apply to Twitter? Why not? After all, what is a blogger?