After building the UI for a reasonably sized web application (which happens to be very heavy in javascript), I found that with around 40 JavaScript files being included into the page and the size of all of the files together caused for some poor load times on anything but a very fast internet connection. A common technique to solve issues such as this is to use a JavaScript compression technique such as js-min, YUI compressor, dojo compressor, and others. Because the YUI compressor gives very good results (better than the others in the tests I saw) and is very easy to use, I chose it.