Without a doubt Twitter has become a leading force in the sharing of information on the web. Whether we look at it as "the poor man's email" or "real time search" or some degree of the two, it cannot be denied that Twitter is the fastest growing product on the web right now and people are adapting to this and creating apps to take advantage of the phenomenon.
To challenge Google Twitter needs to go beyond the friendly chatty social network that helped in its initial growth and move to a serious functioning information source.
We have all heard that Google should buy Twitter - even though their Friend Connect app offers basically the same elements. Sort of sounds like what happened when Alta Vista, Lycos and Excite had the dominance in the search arena - with Excite having the opportunity to buy Google for $1 million - only to see the popularity of Google overcome the competitors with the aid of Bill Gross's invention GoTo which became Overture and was eventually bought by Yahoo. Google had to pay Yahoo a substantial undisclosed amount for using Yahoo's product - though the wheel came full circle and now Yahoo uses Google's PPC system.
Twitter may not have its own method of monetization yet, but its seems others are rapidly offering services to improve your follower numbers or help use the system to profit from marketing messages. Twitter has been testing with a search box, as well as, adding a small text ad box to see how they perform. Their venture capital allows them a little breathing room, but the soon to be 3 year old application may be closer to a way to make money than many think.
The ability to alert people to local problems, or provide very specific local ad messages is an area that Twitter has particular expertise.
Will it bring down Google - no not likely but it could grab a considerable share of its market. Google is no longer the only source of information and people are fast learning that.
We like the immediacy of information Twitter provides and the sources are people we know and trust in many cases. This is a strong element that Google will find hard to counter. Where we will be in five years from now is definitely going to be interesting and Google will be around but I seriously doubt if it will have the strangle hold it has on search marketing it does now.