1. Supplement Pages in Google
The pages in supplemental index are crawled seprately by Google as compared to the regular indexed pages. According to matt cutts the relationship between these two indexes are handeled a bit differently. He did't reveal the all details.
Webmasters should not worried because Matt Cutts blog also have many supplement pages.
2. Paid Links
Google does't allow to buy links in their webmaster guidelines, These websites can be penalised in the future.
3. Outbound Links
The outbound links are good for the internet users as well as for the search engines.
4. Impact of spammy domains which are owned by the same person
The webmasters who owned several apammy domains by the same name will be penalised and it can be penalised for all the domains.
These are some useful statemants said by Matt Cutts for Search Engine Optimization.