That's actually a very interesting question. I've noticed for a while that the people who are best at giving advice to startups tend to be funny. It's not a job where it would be good to be the humorless variety of smart. I think the reason is not that being funny is important per se, but that being funny and having good ideas about startups are so similar that it's impossible to find one without the other.
Would add that humor to me is linked to being liked which is important in getting people to do what you want them to do or listen to you..
And being liked is related to at least two things [1]. One is having lots of people who want to be around you which can be an advantage (you can get people to help you and do things for you it's like being the "pretty" girl).
Of course it can also be a big distraction (you are funny and people want to spend time with you so you are less inclined to stay in side and study or hack at something).
In terms of someone listening to you humor is like an anesthetic that puts people at ease and makes them more inclined to at least hear you out (that is if they don't take you as being a complete goofball). And perhaps the mental state that a good joke puts them in makes it less likely that they will be defensive and opens them up. (An example is my wife who I can never get mad at because she is always following up with humor to anything that goes wrong.)
I could also stretch and add that being funny provides social proof since the group as a whole likes or appears to like the funny person giving advice.
One component in humor is taking an idea out of context. This is in some ways related to "lateral thinking" where you try and brainstorm by randomly changing marketing bits (price, place, promotion, product) to come up with a new way of seeing things. I think some people with a creative/entrepreneurial mindset automate this process in their heads. So you could see humor as a similar creative process to that of some innovators: being able to see the world in a slightly different/skewed way. In one case, it makes you laugh because of the incongruity, in another, it may help you see ideas for businesses where others do not see them.
More generally, I would tend to say that humor is often about finding odd connections. I can easily imagine that being an important ability for giving good advice to businesses.
Jesters were important in monarchies because they could speak truth to power. I think there's a similar idea here: you have to be very headstrong to do a startup, but at times you also need to pull yourself out of that and really consider other angles/viewpoints. If you can couch advice sometimes in humor, maybe it can be an effective way of getting through to a founder who would otherwise have a hard time hearing it.
Although one could imagine a humorless person spending 20 years of his life building startups and thus becoming a useful advisor, despite not being particularly funny. Another possibility is that the humorless type aren't as interested in offering to help.
