what do you mean? The actual *take a screenshot* thingy?
its usefull to display nice setups, prove that you can hack wine well enough to run steam on linux, problems (not with the X server), make images (for essays, presentations, etc) using web based apps.
You can also use it to monitor your monitor
make and chron a shell script to mail you a screenshot of your pc every 10 mins to see if your employes are browsing suicidegirls.com (a nice site btw :P)