The title is somewhat misleading. It's not really a new tax, just a different interpretation/application of an existing tax. I do love how these bills always come under such monikers as the "Main Street Fairness Act."
Lack of regulation is one part of what makes internet-based commerce so great. I wonder if services (ie: Basecamp, git, etc) would fall under the sales tax, further complicating the legal landscape of 'net based tools.
In the state of Tennessee, software development services that I render to local companies is already taxable under a 10% "use" tax (the state has no income tax, and developing software is considered creating something of 'use,' therefore, taxable).