Charlene Li over at Forrester Research says today that search engines such as Google and Yahoo that engage in a game of one-upmanship are missing the big picture — and the real threat to their user base. Based on a consumer survey Forrester conducted, Li says search engine users are not necessarily a loyal bunch, opening the door for specialized search engines to steal users.

I believe that even as the major search players continue to extend their reach, growing consumer sophistication will mean that specialized search will make their debut — and stick. Look at Singing Fish for audio/video search, local-i.com for local search, and Feedster for RSS feeds. And don’t forget that there are already many examples of vertical “search” engines with access to proprietary databases, such as cars.com, Expedia, and Monster. So look out big guys — even as you extend your reach beyond Web search, look out for the little guys who will start chipping away at your users.

UPDATE: Danny Sullivan at Search Engine Watch deconstructs the Forrester item.