I've found some content won't appear/work if ads are blocked. So in some cases I temporarily whitelist a site in AdBlock or Ghostery. With a HOSTS file, isn't that sort of thing a lot more painful?
(I used to use the HOSTS method but stopped for that reason.)
This has yet to affect me to the point of me actually noticing that anything was broken. The worst I'll see is a lot of extraneous whitespace on a webpage where an ad would have been.
That said, frankly, if a web site won't work properly because it can't load content from an ad network, then it's probably not a site I'd want to visit and pull information from.
(I used to use the HOSTS method but stopped for that reason.)