Why Job Boards Share Postings
Virtually every major job board shares at least some of the jobs posted to it with other job boards. The boards each do this to help ensure that they have plenty of jobs postings for virtually every candidate who runs a search at their sites. Some boards, for example, may have a lot of postings for candidates in the eastern United States but not have enough for candidates who are searching for a position in the western United States so they'll pursue crossposting partnerships with boards which are strong in the west but not in the east. By sharing postings, candidates using either board are almost always sure to find multiple positions of interest so they'll be more likely to register, apply to the jobs, come back repeatedly, and refer their friends.
A good analogy is the menu at a restaurant. If you look at the menu outside of the restaurant to decide if you want to eat there and see only one item on the menu that is of interest to you, then you'll be more likely to opt to go elsewhere than if the menu had 10 items of interest to you. Furthermore, if the menu has 10 items of interest to you, then you'll be more likely to come back and refer your friends.
The boards which share postings, and virtually all do, typically disclose that to their employer clients by talking up their network. CollegeRecruiter.com, for example, promotes to its employer clients that it has 11,000 sites in its network. That means that when an employer posts a job to CollegeRecruiter.com that we will send that job to all of the relevant sites in the network of 11,000 sites. If the job is for a sales person in Vermont, we won't send it to the accounting or Texas sites but we will send it to the sites which target sales job seekers and the sites which target Vermont job seekers.
Sometimes these relationships are paid and sometimes they're unpaid. We trade postings with some sites where no money is exchanged. Essentially, we run some of their jobs on our site and they run some of our jobs on their site. When we run a job on another site and a candidate reads the job and clicks the apply button, they're brought to our site to apply. That generates traffic for us. The goal in these crossposting relationships is for our partner site to send about the same number of candidates to our site as we send to theirs. In other cases we are paid by our partner to run their postings and send our candidates to the partner site. That's more of an advertising model under which we're paid to drive traffic to the other job board.
Just wanted to tell you all know how much I appreciate your postings guys. Found you though Google.