It would be interesting to have some numbers on collectibility, though. Both income taxes and sales taxes can be dodged (black-market purchases and out-of-state online purchases are two common ways of dodging sales taxes). There are a number of examples of states raising either one, and it'd be interesting if someone has extracted data on the results.
I'd hazard an educated guess that the percentage of income spent by the poor online is tiny. Both because the above factors and also because the majority of spending for those group is going on rent, groceries, vice (cigarettes and alcohol) and transport which aren't commonly bought online in any case.
Would appreciate any links that anyone might be able to provide for further reading or data related to this topic...
See this press piece by Walmart:
http://news.walmart.com/news-archive/2012/04/26/walmart-anno...
There's also several startups in this space like Fuze Network and PayNearMe.
This is not true in the US, where your debit/bank card is also a VISA/MasterCard fully usable online. Even people with zero credit can easily spend money online. If you have a bank account in the US, there are effectively no barriers to spending the money in it, online.
In practice, you could tax one thing everyone elses (like food) and just wait it out, and all money will eventually route itself back through the taxed exchange. The point of such taxes is to take a fraction of all exchanges.
Though, I'd rather they solve the problem of why a black market needs to exist than try finagling a tax solution on it. You have to go back to the drawing board and ask "what is there a demand for we have artificially restricted such that it is forced onto a black market?" and see that tremendous potential tax revenue for what it is.
I'd suspect that many online retailers would be forced to go down the path of outsourcing most of this using something like Shopify or similar -- it's just a lot of tax rates and calculations to keep track of, not to mention report on and optimize for!
I see a great opportunity for a webservice startup here.
This is one of the companies that collects a giant database of jurisdictions and tax rates, as well as a db mapping SKUs to jurisdiction-specific tax categories: http://tax.cchgroup.com/sales-tax-data/default.htm?cookie_te...
Though I'm sure there is an opportunity to help small companies since most companies who currently need to manage national sales taxes are large (have a presence in every state).
Encouraging savings and reducing consumption might be good things for society, but it seems that they hurt the economy (less trade, fewer jobs) rather than benefiting it.
So the "good thing" would have to come from Congress. Good luck with that.