To begin with, the Startup Visa Act has seen no movement in Congress since its introduction in Congress on March 14. http://www.govtrack.us/congress/bill.xpd?bill=s112-565. COICA and SOPA have received much more attention.

According to the proposed bill, S.565, to obtain and keep a startup visa (valid for 2 years), an entrepreneur must:

a) obtain $100k from a qualified investor, and during the following 2 years, must create 5 or more new full-time jobs in the United States for people other than his immediate family, raise $500k or more in capital, and generate $500k or more in revenue, OR

b) have an unexpired H1-B visa -- this already excludes foreign startups, OR

c) have a controlling interest in a foreign company that generated $100k or more in revenue from sales in the US, and create in the next 2 years 3 or more full-time jobs in the US for people other than their immediate family, raise $100k or more in capital, and generate $100k or more in revenue.

There are further restrictions on qualified investors:
a) qualified super angel investors must be US citizens
b) qualified venture capitalists must be based in the US and have more than $10M in capital

Blueseed makes it significantly easier for foreign-based startups to work in close proximity to Silicon Valley by not placing restrictions on the source of their funds, the revenue they must generate, or the number of jobs they must create.

Startups out there might not want to take the risk that Startup Visa won’t pass, or that it will pass in a form that’s inadequate for their needs (e.g. a permanent requirement for more than X employees would force a startup out of the country if they temporarily are force to lay off people and now only have X-1 employees; similarly, a permanent requirement for a certain level of funding could also hurt a startup).

Secondly, according to the Startup Visa bill proposal press release (http://www.webcitation.org/627BU0HxF), to accommodate this new type of visa, adjustments would be made to the existing EB-5 visa, which grants visas to foreign nationals who invest $1 million towards the creation of 10 jobs:

Under a new EB-6 category, a visa would be granted to the innovative entrepreneur
with intellectual capital, instead of a wealthy foreign investor who is in a
position to buy a visa. The legislation [S.565] transfers an allotment of the
yearly 9,940 EB-5 visas, of which only 4,191 visas were used in FY 2009, to be
granted under the new EB-6 category.
*The creation of new visas is not authorized in this bill.* [emphasis in original]

So any unused EB-5 visas could be transformed into startup friendly visas. In other words, the startup visas would compete with the investor visas for a limited pool of visas.

Also, given the government inertia typical of these matters (e.g. the Comprehensive Immigration Reform has been stalling since 2006), by the time (if) immigration regulations become lax enough, we will have franchised away from the "foreign nationals" business models.

Finally, we’re creating a space so compelling that even if you’re a company without any visa issues, you still want to be onboard Blueseed because it’s going to be the most awesome space in Silicon Valley. The #1 most common country that startups who've filled out Survey of Interest are from is the US.

I hope this answers your question.