However it is just not neglected bikes that have problems, any bike that is ridden regularly and hard throughout the year desperately needs that overhaul before the new season starts. Recently we had just such a bike in the workshop. This bike is one that has been overhauled by us before, not yearly I think we did a frame up rebuild on it 3 years ago, however the bike always is cleaned and lubed on the outside by the owner and kept inside.
Below is a picture of what we found inside the bottom bracket shell, once we had used a breaker bar and 2 of us to get the cartridge out!
Keep in mind that this is an aluminum frame so that is not rust from the frame itself that you are seeing however aluminum does create a powder like substance under the right conditions. This is a mixture of sweat and moisture that finds its way down the seat tube and also the cartridge itself being steel bodied can supply some rust to the mix as well.
Moral of this story is. "If it looks good and clean on the outside, it doesn't necessarily mean everything is cool inside..."