Starting a company has been compared to getting married, and while plenty of people have met their future spouses on dating sites, they don't meet, talk a few times, and then get hitched. Perhaps the missing bit is finding something people can work on for a while without the commitment of a company (sort of like dating...).
Agreed. That's why if you check out the concept of virtual company, it's a great way to start working with someone else with limited committment.
To me, first and foremost, the fact that you don't have any out of pocket expenses is a good thing, it eliminates one barrier to entry. Virtual companies achieve that. In comparison, joining a "real" incorporated startup as co-founder, the first thing you do is split the legal costs and buy your shares. So right there, a few thousand dollars before you even know if you should work together. And there is no "undo" button, unlike virtual companies.
That's also why in the co-founders meetup I ask the presenters to not only present their business, but reveal a bit of their own personality. I believe that compatibility as co-founders comes equally from being passionate about the same things but also being compatible personality-wise (read this http://blog.fairsoftware.net/2009/11/19/first-co-founders-me... for more on the topic).