The original idea behind the Congressional action to exempt online (circa 1995/6 IIRC) from collecting sales taxes was to protect a new technology from having to comply with thousand of different taxing authority.
The internet has grown up a lot since then and there is no rational reason for maintaining the law. It certainly is the case that Congress should act, but of course what Congress should and what the will do are often very different.
Figuring out the sales tax laws for all of the states and locality isn't rocket science. It is certainly no harder than figuring out where you can ship wine and liquor which varies by county in many places in the country.
It is a very minor expense for the big internet companies. Plus when you consider that Ebay, Amazon, Yahoo, and think Google all offer E-Commerce servers for <$100/month all of the major will quickly offer affordable service that will add sales tax calculations, to credit card, pay bill and the shipping calculations that currently offer. The cost for collecting sales tax will be small for even small companies.
There are three reason whys this should happen. The first and obvious one is that state need the money. The second adding the sales tax to the cost will level the playing field for B&M retailers vs E-tailers which I think is generally a good thing. I suspect in my case it will still be significantly cheaper to buy online than local but in a few cases I my switch to buying local.
The final and least obvious one is will is making e-tailers collect sales tax will transform probably close to a hundred million Americans from tax cheats (including myself) into honest (or at least more honest) taxpayers. In the vast majority of states, it is the taxpayers obligation to pay sales tax on their out of states purchases. In some states like California they aggressively go after this (so for instance California residents who buy cars in Oregon (with no sales tax) still have to pay sales tax to CA.) While I imagine 5 or so years ago most people didn't know this I suspect that most people know this now.
I'm probably the only person in Ohio that actually computes and pays "use tax" every year on my state income tax. This is the sales tax for internet and mail order purchases. So, it wouldn't bother me for Amazon (and others) to charge it.
While I commend gindie for doing this, he is the only person I know who does. Even if the tax was only a $1, there is no way I'd have the inclination to go through my records (lousy as they are) to calculate the sales tax I owe for internet purchase, fill out the forms on quarterly or annual basis. Honestly, they'd have to start throwing people in jail for internet sales tax cheating before I'd behave differently.
One of the things I hope we learned from Prohibition, the 55 MPH speed limit, and the drug war is having unreasonable laws on the books cause people to not only ignore them but encourages them to start flouting other laws.