Seo Contest definition that i take it from wikipedia are :

An SEO contest is an activity awarding prizes that challenges search engine optimization (SEO) practitioners to rank themselves among the major search engines such as Google, Yahoo, and MSN using certain keyword(s). This type of contest is controversial because it often leads to massive amounts of link spamming as participants try to boost the rankings of their pages by any means available.

The organizing body of an SEO competition may hold the activity without promotion of a product or service in mind; or they may organize a contest in order to market something on the Internet. Participants can showcase their skills and potentially discover and share new techniques for promoting websites.

Create backlink campaign (link building) is the must to get more higher position to fight on search engine.