Paid links
 

Despite the fact that Google fights against paid links, backlinks still remains the most significant factor for seo as links are base of site promotion. Just high quality backlinks have strong influence on page rank.
Content, links in social networks, forum posting, guest blogging and so on can be just additional measures.
So the question is to buy or not to buy backlinks or forget about seo and follow Matt Cutts rules? how do you think?

Don't buy back links and never forget SEO..SEO is must..