How do you tell someone that their idea isn’t very good, or that they aren’t experienced enough, or the team isn’t going to work out? If this is to happen, obviously the person saying no has an opinion on the matter based upon a little experience in the area. If you have to tell someone no, be upfront about it by saying “no”. Don’t talk around the subject, don’t allude to the “no,” and don’t tell them that it is a good idea hoping that they will simply go away.
Tell them that you don’t think their idea, or experience level, or team are good (or good enough). Tell them why, be upfront and be specific. I assure you, they will appreciate it.
Importantly, by saying no you aren’t making a statement about them as a person and they shouldn’t take it that way. The opportunity just doesn’t fit with your focus, interest, experience, etc.
When I tell someone no, I definitely try to do the above. Sometime to more or less success. I always sincerely tell them that “I do love being proven wrong!”

I’ve been on both side of this… as an entrepreneur being told no by advisers, investors, colleagues, etc. And I’ve also been pitched ideas by fellow entrepreneurs…
It sucks being the one to shoot down somebodies ideas, but it is far worse seeing somebody stumble way further than they should have because people were too afraid to be critical and to let them know their honest thoughts. You don’t need to be a Simon Cowell about it, but there is real value in being a grounding voice to people who aren’t hearing anything but empty praise.
I think the best approach is to be honest. It does nobody any good if you dislike the idea and don’t let the person know why. The key part of that being how you give the person constructive criticism.
I actually wrote something last year about the ego needed to be an entrepreneur…
In any form of sales you need to have confidence. You have to convince another person in the value of the product you are trying to sell them. As an entrepreneur that product often isn’t a disconnected something, but your idea and a very personal part of who you are.
http://younggogetter.com/2007/03/23/e-is-for-entreprenuer-and-ego/
To answer your tweet, I’d take NO over MAYBE any day.
1. The person is probably much more likely to provide good criticism if they are trying to back up a no.
2. Have some balls…
3. I love to prove people wrong.
“No” is always such a better answer than “Maybe” — saves everyone time, and helps people re-focus. Of course, it probably necessitates another 60-90 seconds to explay “why”, but again, I think it saves a lot of time in the long-run, be it in e-mails ignored or deflected, or in recurring Maybe’s.
A hard “NO” sucks, but a soft “no” (a maybe that fades away without explanation) is worse. It leaves you frustrated and full of self-doubt.
Personally I would rather hear the investor’s objections. It is better to have someone tell you that they think the product is flawed or the market aspirations are unrealistic or the team isn’t right or whatever. Targeted, constructive criticism is helpful. Maybe we do have weaknesses. And maybe we can do something about it, if we know what it is.
That said, as entrepreneurs we need to know how to take criticism. I believe one reason criticism is not always shared is that entrepreneurs take feedback as objections that should be overcome and can become argumentative. So, my suggestion is that even if you don’t agree, just listen! Then ask questions like “Do you have any suggestions on how we might address that issue?”
And definitely thank them for their quality feedback, even negative. I remember a few years back flying down to meet with Palomar Ventures either in their Palo Alto office. Our startup was pretty far afield from their focus area and it was a long shot. As we kind of expected, they passed, but the VC still spent two hours with us and she had actually read the ENTIRE business plan including business projection spreadsheets in advance – pointing out several small errors which were immaterial but embarrassing nonetheless.
She also followed up the meeting with a detailed email that provided extensive feedback. It was invaluable and made our subsequent pitches much stronger. It also gave me an incredible amount of respect for her personally.
So mad crazy props to Amanda Reed at Palomar Ventures. To mix metaphors, she was both a tough cookie and a good egg. The world of investors and entrepreneurs would both benefit from that kind of dialogue. It is far too uncommon.