Google became successful very fast because it offered a simple solution to a problem we all had, namely finding results on the internet. It gave us the best results and it was extremely simple to use. And these reasons for success could also be ways for someone else to take that business.
Today there are many search engines that do the same job, and some arguably give better results than Google. And they are all just as easy to use and offer a similar UI.
This is why Google is investing in so many auxillary programs such as spreadsheets and money managers, and offer them for free- so people will continue to go to Google for their needs.
Dharmesh Shah has a post about this topic which is very interesting. It really would be easy to switch from using Google to another search engine for most consumers. Dharmesh brings up some good points about why it would be so easy to switch;
Low Training Investment:
Low Customization Investment:
Better Results Are Obvious:
Obviously other search engines have been trying to woo people away from Google, but they’re offering a similar product. What if MSN or Yahoo or Ask or another search engine actually developed a better user experience with better results and promoted it- would it be difficult to move away from Google?