David Hobbs has written an excellent post about how managing a website needs to change as your site grows. He draws a comparison with traveling alone vs. with a family: spontaneity vs. stability. To quote:
But, as with websites, this really isn't about one mode of travel being the "right" one is it? If you're just out of university backpacking around Asia, then sure be spontaneous. If you're single traveling on business, then take advantage of features that might not be worth it to the backpacker (like taking a taxi ride straight from the airport to hotel, rather then a series of public transportation that might make sense when backpacking). If you're traveling with a family, then maybe a more planned approach with less stops makes sense. But the point is that there is no single "answer" to the best way to travel, like with websites.
David makes the point that the supporting organization has to adapt to the needs of the website. Some companies transition more proactively and gracefully than others. In the post, David mentions "subsites" as added complexity. I think this is interesting because many organizations look at subsites (marketing landing pages, campaign pages, product sites) as a way to escape the complexity of their main site. It's a little bit like a weekend get-away without the kids. But over time, these subsites become part of the overall web program's complexity.