Actually yes it DOES hurt.
A flat & automatic NO suggests a few things:
Firstly, arrogance that you are better/busier/more in demand than the person asking.
Secondly, that you're not willing to negotiate under any circumstances - either now or in the future.
Thirdly, that you're a pretty rude person to be with/deal with.
And that's all very fine, except when it happens one too many times or with even just a few influential people or when your star starts to fade or simply when you wish to avoid Bad Karma.
And especially when you preach about the importance of 'Tribes' and 'Leadership'.
I saw the brilliantly charismatic social entrepreneur Tim Smit (founder of the Eden Project) speak at the Institute of Directors a week or so ago and he said that he ALWAYS accepts every third invitation. And as a result has found himself judging vegetables at a country show & speaking at a WI meeting as well as all the high powered events. Keeps him grounded apparently.
Yep we're ALL busy busy busy, but my advice would be: leave some space in your life & diary & heart to practice saying YES just once in a while.
Especially when it is to your biggest UK fan, who has so far sold thousands of copies of your books for you via raving about you to every entrepreneur she meets/speaks to at events - and who has just launched an events division and has invited you to come speak in London.
If you're wondering what the hell I'm on about, see Seth Godin's latest blog post "It doesn't hurt to ask".
Evidence a certain person has just lost sight of who is the customer.