Probably a stupid question...

[Halfdeck]

I don't understand why you point out the difference... are you saying one is more important than the other?

Not necessarily, just that in general, many items listed under "design" is associated with user-friendly design (e.g. "create a useful, information-rich site", "think about the words users would type to find your pages", "Offer a site map to your users") and crawlability (e.g. "The Google crawler doesn't recognize text contained in images.", "be aware that not every search engine spider crawls dynamic pages"), while items listed under "quality" falls under search engine (over)optimization (e.g. "Avoid tricks intended to improve search engine rankings", "Don't participate in link schemes designed to increase your site's ranking or PageRank", "Don't employ cloaking or sneaky redirects.")

In other words, a page with too many links may not be all that user-friendly (e.g. huge LL category page forcing a surfer to scroll down to find free site listings). Googlebot may also prefer to crawl pages with moderate number of links or limit the number of links it crawls depending on site trust (speculation).

I'm not saying a site with 2000 links per page isn't going to trigger some sort of a flag (I'll have to test that). But if Google assumed that any page over 100 links is more likely to be spam, that would result in many high-profile false positives, including cnn.com (~142 links), amazon.com (~203), and ebay.com (~143).

There was a rumor about the use of sitemaps to spam google and that it could be bad to use them to get indexed becouse of that.

Rumors usually hold no water.