I've been working on the internet industry for over 10 years now, I started back when it was "in" to make all kinds of crazy animations in Flash and the web was not about the content.
There are several things I don't like about the web, like IE6, stupid comments, browser prefixes, etc, but there are only 3 things that consistently get on my nerves along the years: spam, invasive ads and preloaders.
If spam is the cancer of the internet, preloaders would be like a bad cold, that won't let you get off your bed.
In the Flash days, they were somewhat necessary because it was more about showing a cool animated video than the content, now, we have no reason. Preloaders were a tool to make the waiting not so bad, but there shouldn't be a wait. And if there is, that something you are waiting for has to be worth it.
We are getting to a point where JS and CSS are so advanced that we want to do the same things we did with flash 10 years ago, and then having to put preloaders again because we went too crazy with it, and losing focus of the content again.
Optimise and strip down to what's really necessary and get rid of the evil preloader.