Who knows more about building a house?  Professional architects and carpenters, or someone who reads the real estate section of the paper every day?  Who would you prefer to perform neurosurgery on you? A professional neurosurgeon who has spent the last 20 years of his life studying and practicing this one thing, or someone who just spent months researching brain cancer because their father was diagnosed recently?  

While enthusiasts are almost always more devoted and better informed, specialists with experience are almost always more qualified to make decisions about what should actually be done.  

That's not to say that the netroots aren't an important, dynamic part of politics in America.  Politics is different from carpentry - as citizens, everyone has a right and a duty to hold their elected leaders accountable.  I like to think of the netroots as democracy's housing inspector.  Sure, they don't know the best way to build a house, or where to buy the supplies for the house, or who to hire to get the job done right.  But they can certainly see when the foundation is rotting, and raise an alarm about it until something is done to fix it.