When Al (Sharpton) Franken got caught not paying taxes in states where he had done business or had a residence, I realized the same applied to me.
I had no way of knowing that the many speeches and consulting gigs I had done all over the U.S. made me liable for taxes in the states that have or had state income taxes.
Turns out that state tax authorities only go after prominent people or get incensed when some blogger calls their attention to the unpaid taxes, as is the case with Franken.
I'm not suggesting that there be any consistency in state taxing, I'm suggesting that the states with income taxes form some central collecting agency that makes sure each state tax form inform us non-CPA's what the rules are for paying other state's taxes.