When you say "server based searching" I assume you mean things like Google's web search. It's fast because they dedicate tens of thousands of machines to storing the index and executing the queries. They can do that because their millions of users are all searching the same data set (the web). Dropbox couldn't do that because each user would be searching a different data set (their own files).<p>The fact that it's run on a server machine and not on a desktop machine has little effect on performance, and it probably doesn't make sense for Dropbox to provide the resources for good search when your desktop should be able to do a fine job of it.