institutional context - how are genre channels commercially viable?

as genre channels are normallly owned by a large companies (for example EMAP, Viacom International and GCap Media) they have multiple revenue streams, and therefore do not have to rely on one channel for profit. Many will own not only a television channel but a radio sation and/or magazine, possibly all of the same name and about the same genre.
another way in which genre channels are commercially viable is that they are very attractive to advertisers, for example Creative Zen. this is because the channel is targeted at a specific audience so the advertising can also be aimed directly at this audience. As many of the channels are owned by the same companies, advertisers will have a wider range of channels, and therefore audiences to attempt to sell their product to.