You don't necessarily need to use it since it is all freed at the end of the script. But, as an example, I use it in a very long running script of mine that makes lots of queries. I had to bump up the script execution time from the default so this script would run. This particular script makes about 100 queries from 6 different databases. I free each result when I am done with it just to make sure memory isn't an issue.....
Matt Wade
codewalkers.com