I personally think the last one has the right shape. However, I'm concerned about putting the 'diet' in there, and about having the web address on it.
This is going to be used on letterhead, which will have the web address on it anyway, which I feel is a bit superfluous. Also, if it's going to be used online to link to the site, clicking it would take you there anyway. If we're going to use it on pin badges, etc, which I think will happen soon (in my mind at least) anyway, then definitely it needs to be there! 🙂
Re: the 'diet' and people not knowing what DiDkA is:
I think we're hoping to build a form of 'brand identity', so that that symbol becomes synonymous with what DiDkA is, and that the symbol will MAKE people ask questions if they don't know. I worry that putting the 'diet' there will make the whole thing too 'busy', and not give enough white space. I think I've mentioned this before, but the actual 'text on a symbol' thing is not something I'm a big fan of, because I think the shape itself should be strong enough to speak for itself, especially if we're launching it along with the site, and a massive evidence gathering campagn.
So in my mind, the best combination would be the shape and spacing of Am's last posted one, but without the diet, and the web address just saying 'DiDkA'.
This isn't meaning to offend anyone, and I REALLY hope no-one takes it that way. Everyone's opinions are just as valid, and I just thought I'd pop mine in! 🙂