Affiliate networks that already have a number of advertisers usually also have a large number of publishers. This large pool of publishers could be potentially recruited. There is also an increased chance that publishers in the network apply to the program by themselves, without the need for any recruitment efforts by the advertiser.
Relevant sites that attract the same audiences as the advertiser is trying to attract, but are not competing with the advertiser, are potential affiliate partners as well. Even vendors or existing customers could be recruited as affiliates, if it makes sense and does not violate any laws or regulations.
Almost any website could be recruited as an affiliate publisher, although high traffic websites are more likely interested in (for them) low risk CPM or medium risk CPC deals rather than higher risk CPA or revenue share deals.
