I'm super glad you asked.

http://lessig.tumblr.com/post/14357153028/the-grant-and-franklin-project

When representatives are dependent on money for their campaigns, they're therefore dependent on people with money for their campaigns. They're not depending on the people they represent who can't afford to fund their campaign; they're depending on people who have $500, $1000, or $2,500 of expendable cash to throw around. This can skew how they represent their constituency. Example: Lamar Smith, R, 21st District of Texas, Sponsor of SOPA.

If you look at that district map, you must ask yourself: why would they care so much about internet piracy? They're not Hollywood, They're not New York; the economy of the 21st District probably isn't stifled by Piracy much (perhaps Austin... but that's a stretch). It doesn't make much sense that their representative should introduce SOPA.

But then you look at Lamar Smith's Money Trail.

Sudden Clarity, Clarence? Now we see why the representative of the 21st district of Texas cares GREATLY about Internet Piracy, even when his district may not. The question begs: Is he representing his district well?

I personally believe that Lessig's Grant-Franklin proposal would stifle this influence of lobbyist money. Representatives wouldn't just listen to him-with-the-fattest-wallet, but to the people they represent - just like they should in a democracy.

Again, give "Republic, Lost" or at least "One Way Forward" a read. Those explain this much better than I could.