As a CPA, this decision is a head scratcher. It is contrary to prior cases and tax law principles used to establish what "creates taxable nexus." In other words, what about the transaction gives the taxing jurisdiction (state in this case) the right to tax the transaction.
California lost a case that said CA could not tax retirement benefits of state employees who moved out of CA. The rationale presented by CA was that since the money was a benefit earned while living in CA and it was paid from CA to the retiree, CA should have the right to tax it. CA lost, and their case, at least based on tax law principles, was a lot stronger than this case.
With this new case weakening past tax law principles and precedent, I expect states to get a lot more aggressive in taxing anything they can get their hands on. This case surely makes it more likely for states to prevail in new efforts.
Odds are this case will affect a lot more than just sales tax assessed against online sales. Hold on to your wallets.
At least in my mind sales tax is a point of sale tax to consumers charged at the time of purchase and income tax is withheld at the time income is received. It sounds as if CA in essence was asking to pre-tax income to circumvent the "at the time it is received" aspect of income taxation.
It would be nice if this lead to a move towards a straight consumption tax so we could do away with the inequitable IRC so every individual and business was taxed on a level playing field.