There is a very interesting article about this question: http://bits.blogs.nytimes.com/2009/05/14/do-web-entrepreneurs-still-need-venture-capitalists/

It basically says that given the lower cost to create web companies, the current venture capital model may not be attractive enough for those web entrepreneurs. It gives some examples such as the iPhone Apps developers that do not need a huge  amount of money to create their products. 

However, it ends the article saying that is why some venture capital firms are changing its strategy by creating special funds for this type of development or some VCs creates smaller fundings specially designed for these web entrepreneurs.

I believe it is a must read for web VCs and entrepreneurs.