Obviously before these type of meetups entrepreneurs were successful in creating companies so it's not a requirement. But there is a lot of value in getting out there and interacting with people, it's only networking for networking sake if that's how you approach it. A great time to talk about what you're doing is exactly before you have an actual viable product. Personally if I would have waited until everything was 'ready' I would have missed some critical connections. The risks are zero (well the reputation thing could be real, so have something to say), the potential reward is actually high.