goodroi - 11:31 am on Oct 31, 2012 (gmt 0)
Simple answer - Big brands typically generate big quality signals that the Google algorithm is currently rewarding.
More detailed answer - Big brands spend millions of dollars on tv commercials this leads to people organically talking about them and linking to them. Now they have a huge amount of backlinks. Also these big brand websites have a huge amount of type-in traffic, that leads to very attractive usage signals. When you add in the contests they often run which generates huge volumes of user generated content, reviews and the teams of editorial writers they often employ - they often have good content signals. Even if they are lacking in one ranking area their other ranking areas are often strong enough to compensate.
Solution - Big brands have big budgets but they also have big waste. To make a change on these big brand websites you often need to have multiple conference meetings. Small guys like me don't need to waste time on multiple conference meetings and I can move faster. Also I know tv commercials can help but they are a terrible ROI. Instead of blindly throwing money at the problem I use my creativity. For example I identify a good group of relevant bloggers with strong readership and offer them an interview with me. This provides free & interesting content to the bloggers so they agree and gets me backlinks and exposure which often leads to even more backlinks from bloggers I don't even contact. With good creativity you can overcome the big brands, I know because I have multiple websites that outrank Fortune 500 companies.