Fyi Its not sales tax congress passed with paypal, it is income tax. This year the IRS began requiring sites like paypal to issue 1099s to some of its users.
You will only be issued a 1099-K from paypal if you have $20,000 in goods and services sales and completed 200. So most wont run into it, however I suspect they are paying a way for the future where all sales will be reported on a 1099-K.
If that happens it will be crucial for people to document the cost or cost basis for the goods they have sold on ebay sites as well as the fees they paid...