What is size of vertical search engines and social search engine market?

http://www.seochat.com/c/a/Search-Engine-News/Healthy-Future-for-Vertical-Search-Engines/

http://www.seroundtable.com/archives/cat_other_search_engines.html

http://www.eleganthack.com/archives/2005_06.html

http://www.websearchguide.ca/netblog/archives/cat_search_engines.html

hope these help