Yet this isn't exactly what this article is talking about. I agree with the article in general-- that "stealth mode" is usually unnecessary and isolating and that people simply stealing an idea is pretty rare to non-existent. What's even more rare is someone successfully stealing an idea. Usually anyone mediocre enough to want to lift someone else's idea isn't up to execution.
What I'm talking about here is more the personal one-on-one long-con... the predatory narcissistic types who hang around the business community, make grandiose claims, and then deliver nothing or worse mooch time/money off entrepreneurs. Stealth-mode won't protect you from this. Street smarts and skepticism will.
Edit: Here's a bit of advice for avoiding these gadflies:
Get specific. Who are you? Why are you interested? What do you want to do and what do you want in return? If they claim to be an investor, are they an angel? Accredited? With what firm? What else have they invested in? If they don't get specific back, they are blowing hot air.
Avoid "business consultants" who talk about "accelerating" you or "taking you to the next level" without getting very very very specific about how. Most of these people are bozos. Even if they're not bozos, usually they are not who an early-stage startup needs.
If someone talks fast and uses a lot of buzzwords, this is a bad sign.
Check references carefully. Keep in mind that narcissistic self-promoter types can be extremely creative about making a nothing look like a something.
If you do get involved with someone, drop them and move on if they don't deliver. Don't ever take hot air as a substitute for real results.
If you hang around the startup culture and talk up your idea you will run into these people and they will at the very least waste your time.
Also: the "scene" will kill your startup. Concentrate on executing and ignore the "startup scene."