I can see the convenience factor in talking freely, not asking for NDAs, etc. Oh, if life were that simple…
First of all, if you have a provisional patent application you cannot disclose openly without losing all patent rights. Investors, lenders and cofounders, all value patent rights. So for this reason alone, giving your idea away is not realistic.
Then you say: “…a pointless NDA”, that is a legal opinion. Try running it by your attorney, I’ll bet she doesn’t agree NDAs are pointless.
There is also privacy. You don’t need people to scoff at you or your idea. For example, when Sara Blakely was developing Spanx, the idea of footless pantyhose might have seemed frivolous or worthless to many. Here is her actual quote (from Inc. magazine): “ I kept my idea to myself. The only people I told were patent lawyers and people in the undergarment industry. Ideas are fragile in their infancy, and I sensed that if I talked about it with friends, I might be discouraged.” Right on!
Last example. Zuckerberg apparently did not copy the facebook idea from the Winklevoss twins, but knowing about it bought him time to stymie them, while rushing his own version to market. It would certainly appear like openly discussing their idea cost the Winklevosses years of litigation and a relatively meager payout. How do you think the story would have played out if they had asked Zuckerberg for an NDA or a work contract?
In conclusion, I think there can be some middle ground. Depends who you are talking to. You can withhold some key information, I will leave you with a quote from Paul Graham/ycombinator.com:
“ You may wonder how much to tell VCs. And you should, because some of them may one day be funding your competitors. I think the best plan is not to be overtly secretive, but not to tell them everything either. After all, as most VCs say, they’re more interested in the people than the ideas. The main reason they want to talk about your idea is to judge you, not the idea. So as long as you seem like you know what you’re doing, you can probably keep a few things back from them.”