I think starting a small side project with 'random people on the internet' is a way better idea than 'searching for a cofounder on the internet', as it's likelier to actually produce something interesting and really give you an idea about the person who you're working with.
+1 especially for that second part. I feel like you can easily evaluate other people's competence after working with them for a month or two. You don't need to spend 40 hrs / week with them to know this, it's more of an evaluation over time type thing.
