onStartups has a few points on why it would be potentially easy for users to switch away from Google Search. The main points he makes are:
1. Low Training Investment
2. Low Customization Investment
3. Easy Experimentation
4. Better Results
These are precisely the reasons most users moved to Google in the first place. In any case, general search on the net is a commodity that can no longer be leveraged on its own. The future trend will be towards integration of search into other interactions on the desktop, the enterprise and the net. And do these points hold good in those scenarios as well?