Last year I received an email inviting me "to take part in a revolutionary new search engine." I was offered to be a guide at ChaCha, a new search engine that uses human guides to help users find what they want. Amazon.com Inc. (NASDAQ:AMZN) CEO Jeff Bezos invested $6.5 million in ChaCha. Today, with 30,000 guides (I never signed up) and expecting 300,000 by June, the founder, Scott Jones, is taking ChaCha one step further -- his goal is to make ChaCha the search engine of choice for cell-phone users.

ChaCha will be available at a toll-free number, with easy searches handled by voice-recognition software and more complicated ones going to ChaCha guides. The guides will enter the results of their searches into a voice-recognition database for future users. While users wait for the guide, voice ads will be played. According to Jones, cell-phone providers will replace 411 services with ChaCha by 2010.

While Google Inc. (NASDAQ:GOOG) is the obvious name each time Internet search is mentioned, ChaCha may actually see competition from Microsoft Corp. (NASDAQ:MSFT). After a few days of rumors, Microsoft said it will buy Tellme Networks Inc., a provider of voice-enabled mobile search, directory assistance and computerized, speech-driven customer service hotlines.

Microsoft's plans for Tellme's technology are vast and not limited to mobile search but to applications for the home (operating the TV for example), car (getting directions for the nearest gas station) and Microsoft Office applications as well. If one day this technology works smoothly, Google and others would have some catching up to do.

I've always seen voice-activation as the natural progress of current technology and even wondered in the past if Microsoft wouldn't indeed be the one to bring it to successful fruition. Today, we are one step closer.

"Save."

"Publish."

A piece in Monday's New York Times discussed up-start companies seeking to create new search engines that are better than Google. The most interesting threat may come from Wikia (the start-up of a founder of Wikipedia), which will try to create a search engine much as Wikipedia was created: with the help of programmers and users all over the world. Since 2004, venture capital firms have invested $350 million in 79 search-engine related companies. Jeff Bezos, founder of Amazon, has invested in ChaCha, another search-engine start-up.

Google (NASDAQ:GOOG) investors will want to pay attention to the number of competitors lining up with the goal of toppling Google. Remember, Google began its rise to dominance over Microsoft, Lycos, and others when two Stanford Ph.D. students started the company in 1998 in a friend's garage. All it could take for Google to be ruined is for two more college students to come along and invent a better search engine. I see that as being the primary long-term risk factor for Google investors. In 25 years, will Google still be the "World's Best Search Engine"?