Google spam doctor Matt Cutts does a 20 questions type post and reveals a few nuggets:

Why PageRank Still Matters

Q: “My sitemap has about 1350 urls in it. . . . . its been around for 2+ years, but I cannot seem to get all the pages indexed. Am I missing something here?”
A: One of the classic crawling strategies that Google has used is the amount of PageRank on your pages. So just because your site has been around for a couple years (or that you submit a sitemap), that doesn’t mean that we’ll automatically crawl every page on your site. In general, getting good quality links would probably help us know to crawl your site more deeply. You might also want to look at the remaining unindexed urls; do they have a ton of parameters (we typically prefer urls with 1-2 parameters)? Is there a robots.txt? Is it possible to reach the unindexed urls easily by following static text links (no Flash, JavaScript, AJAX, cookies, frames, etc. in the way)? That’s what I would recommend looking at.

The Penalties for Selling Links

Q: “If one were to offer to sell space on their site (or consider purchasing it on another), would it be a good idea to offer to add a NOFOLLOW tag so to generate the traffic from the advertisement, but not have the appearence of artificial PR manipulation through purchasing of links?”
A: Yes, if you sell links, you should mark them with the nofollow tag. Not doing so can affect your reputation in Google.

Best Time to Be a Cuttlet

Q: “Are you planning to visit/speak in the UK at all in the near future?”
A: Sadly not. I’m hitting the Boston Pubcon and SES San Jose, but I can only do 4-5 conferences a year.

***Highlights are mine

Via MattCutts.com.