If you want to start a business, you should get out of your comfort zone. Finding a co-founder on an online platform is the opposite.
Get involved in your area's tech (or whatever your startup is about) scene and find a partner. That validates your idea, too. If you can't find a co-founder in real life, you may need to change your plan.
Ordinarily I'd agree... but as another commenter pointed out, there are issues with small towns... but there's also a time-issue involved.
I created this idea because I'm a hacker, and needed to find business guys... it's taken me a year of joining every entrepreneur/networking group in London - ad I'm now starting to be confident that I know which ones to bother with and which to avoid.
I can imagine that it'd be even worse prospect for a business guy trying the other way around... which of five hundred "user groups" would a know-nothing business guy join to go find smart hackers that can get things done?
As a newbie, you'll join a lot of the wrong groups... and waste a lot of time at them. The two different crowds have an extremely small overlap... this site is intended to cut across the networks (well be going to networks on either side), and cuts through a lot of the time spent searching.
ie - first find a few people that might match your needs, then go join their network and see if you like it (kinda like the "first date")... then see where it leads from there.
Some areas don't have scenes relevant to a particular idea. Believe it or not, random small towns do occasionally produce the odd skilled hacker, who is then geographically isolated and needs an online way of connecting with the rest of the tech world.
Get involved in your area's tech (or whatever your startup is about) scene and find a partner. That validates your idea, too. If you can't find a co-founder in real life, you may need to change your plan.