I think you are
a 404 page.
Unexpected, people hate me.
A 404 page often appears unexpectedly when you were looking for something else, and it's usually annoying to find one since it means you can't get what you were looking for.
Some seek me.
Some people have created collections of cool 404 pages.
I am found when others are not.
A 404 page means "page not found" - it's found when other pages aren't.
I am more than double what is wanted.
What is wanted (apparently) are the 200-and-something pages, which "indicate the action requested by the client was received, understood, accepted, and processed successfully." In particular, the 200 page (see Hint 2 below), and 404 is more than double 200.
this whole idea is specific to the realm of the internet.
what people usually want is 200 OK, the "[s]tandard response for successful HTTP requests". (Thanks to @wl for help with this one.)