There are certainly VCs that would take on large entrenched companies. VCs invested $33 million in Cuil, for example, even though Google had cornered the search engine market long before. And VCs fund companies that require huge capital investment, like medical devices and alternative energy. But both of these issues are big red flags that will make it a lot more difficult to get your company funded.

In a situation like this, I'd expect you'd need to convince an investor that (1) you have a sustainable competitive advantage against the big players, so they can't just take your idea and destroy your business, (2) your business model can generate enough profit to justify the outlandish capital requirement, and (3) you have the right team to make all that happen. #3 is a lot easier when you don't have such big hurdles with #1 and #2.