The problem with huge job boards like Monster or the aggregation that Arrington envisions: There are too many ads. Its a shotgun approach. If you want to hire just anyone, that will work. But if you want to hire the right person then youll need to do something different to reach that person. You need to hang out where they hang out. You need to like what they like. You need to aim accurately. Throw away the shutgun and strap on the rifle.
Targeted individual job boards work because they speak to specific audiences. Were picky about which sites are part of our Job Board network (Signal vs. Noise, Zeldman.com, A List Apart, and the Ruby on Rails Weblog). The people who read these sites care about beautiful code and beautiful design. If you care about these things and you want to reach people who care about these things then you post a job on our job board.
If you want to reach executives interested in broadband, wireless, and technology, you post on the GigaOm Jobs board. If you want to reach someone interested in new company/product launches and the other stuff that is posted on TechCrunch, you post on the CrunchBoard. Yes, theres some overlap between those audiences. But there are also significant differences.
Remember, where you post your job says a lot about your company and the kind of people you want to attract. If you want to toss your job in front of anyone and everyone, post it at Monster.com. If you want to place your job carefully and in front of the right people who care what you care about, then post it on the job board that most accurately reflects your companys attitude/approach. [Signal vs. Noise]