Blogs and wikis both enable the sharing of information by groups of people and provide a platform for feedback. The difference is that blogs do it in the form of comments, where the identity of the commenter/s is known,  while with wikis the users directly edit the content of the given pages.
While a wiki is a type of content management system, it differs from a blog or most other such systems in that the content is created without any defined owner or leader, and wikis have little implicit structure, allowing structure to emerge according to the needs of the users.
 To quote John D. Sutter in Wikipedia: No longer the Wild West? , the idea is that "crowds of people can create the news, share information and collaborate on online projects." According to Sutter, Wikis operate under the  belief that "crowds of people are able to produce a usable and accurate body of information." However, recently the popular encyclopedia, wikipedia, which has drawn criticism for inaccuracies, says it will try assigning editors to some of its entries. These trusted volunteers likely would have to approve public edits before they're published to English-language stories about living people. Some see the move as a shift away from Wikipedia's core values and a sign that the public isn't able to produce accurate online content. Others see it as an unavoidable need to put some order into the chaos of information as online wikis become more complex.
 As for blogs, as mentioned in How can we measure the influence of the blogosphere, they are characterized by regular, date-stamped entries (timeliness)in reverse chronological order, and as wikis, may also include links to related news articles, documents, and links to related blogs(blogrolling) an archived entries (old content remains accessible).
The article Wal-Mart Tastemakers Write Unfiltered Blog tells of how the little-known merchants of Wal-Mart regularly blog about the products the store purchases. Their blogs are very candid and personal, and therefore useful to the store's customers. "Wal-Mart says the Web site helps buyers solicit quick feedback from consumers on the merchandise — and shows a softer side of the giant company."
Blogs are collaborative in the sense that they can be used as platform for online discussions. Each post has a time on it, and the posts are arranged in reversed chronological order, just like conversations.

What is the social "search efficiency" that the current publicly available filtration technology allows in social networking sites? 

The general aim behind my proposed research project is to attempt to  measure and address the level of social "search efficiency" that the current publicly available "search filtration" technology allows - in other words, how feasible is it for a given person to quickly locate specific types of persons based on the common criteria such as in terests, personality or physical appearance. Furthermore, this study could serve as the basis for future research with more advanced and detailed analysis that could hopefully be used by software and web developers to improve the publicly available search tools.