I personally agree with taxing Amazon (more).
Two difficulties with it though:
1) If people choose to simply pay the tax, what more can you do?
The tax would be pretty high for it to be worth me taking time off from other activities to go into town, park, go into a shop on the offchance that they happen to have the thing I want, repeat for however many times they don't have the thing I want and have to go somewhere else.
2) Would it only apply to online business over a certain size, or all online businesses? If the latter would it not penalize small independent traders?
But if not, would you not simply end up with shopping being dominated by lots and lots of small, independent, online retailers?
Would this not be a worse situation - as you would still have online shopping, but just a multitude of small, crap, badly-written websites and different attitudes to delivery, customer service, and returns - rather than one.