Its pointless, unless you have something unique (as a dir owner)
majority of these start-ups are to:
Make fast cash - which is crazy....
Making fast cash from any directory is the wrong way to go about it. Ofcourse some have done this, but its not an option anymore as anything general is perceived as not targetedfor specific businesses, and we have general search engines which are superior at bulk-traffic delivery. I think some general dirs are useful for info hunting, but largely dirs are used for weblinks which helps in ranking - and I think this is the only benefit left to advertising in one - unless its very special and can deliver targeted prospects/buyers.
The dir must have great value and serve a particular market better than general directories can, and this is about converting certain users into buyers, which cant be done with all-purpose websites - traffic is too un-filtered you see.
The SEO route is the way to go here, but you'll need one heck of a slant for a directory to work these days. Potentially, and its a big IF, IF the good dirs (general or niche) can gain enough presense, it may stand a chance of making some cash, but I'd forget any dreams about you becoming a millionaire from one.
I see directories as a SEO driver for paying advertisers, and as part of an already large website group or portfolio, thus acting as an extra traffic offering - I think this is the only way to go now.
The good directories will get insane pageviews, and like I keep saying it only the specialist ones that can do this. Ths is the way to go, but downside is its insane effort trying to set up such a beast - although its possible. But it comes back to having that idea, as just any old idea wont work period, which is the mistake everyone makes.
I spent £11'000 on a directory, setting it up, the crazy hours involved, filling it by hand, getting links and contacting advertisers, and my conclusion is although I made some cash, I never got back my original investment. Although, I did get other rewards that even normal businesses will never see, but then again I'm very good at what I do and made sure I had a decent plan.
But you need to be prepared to take a loss, and be comfortable with that, if not, then dont set up a directory, seriously you'll lose out big time if your inexperienced.