On Friday, Congress came one step closer to imposing a federal "internet sales tax" on any internet purchases by agreeing to amendment that more or less indicates strong support for a more comprehensive internet sales tax down the road. This kind of tax has been pushed for years mainly by two key constituents: (1) big box offline retailers who think that the online guys are only beating them because they don't have to charge a sales tax for out of state purchases (2) local state governments who think they're being ripped off by not being able to collect such taxes.
There are still some hurdles in the way, but it's becoming clear that this kind of tax is inevitable. The amendment passed 75 to 24, so it's got plenty of support. Max Baucus, who heads the Senate Finance Committee which could kill such a bill if it had less support, has already noted that his state, Montana, has no sales tax at all, and he's a bit ticked off that Montana residents may need to start paying sales tax online. Still, as the article above notes, Baucus's ability to block the bill via the Finance Committee is limited due to the size of the support among other Senators. I've yet to see a compelling argument for why such a tax makes sense -- other than random state governments insisting they need the money -- but at this point it seems almost inevitable that it's going to happen.