Sky, rockfairy,
Indeed, it is a very useful feature. It has already been implemented in the Gold Membership program, which will be launched at the end of this month. Gold Membership is an optional, paid upgrade of your account, which will introduce many new features. This will allow us to continue to support and improve this site.
Some of the features will include:

Unlimited score. All regular accounts will be limited to 20 000 points and Gold members will not have this restriction.

No more banner ads! Gold members will not see banner ads, contextual ads, or pop-up advertisements anywhere on the 123facts.com website. Pages will open much faster and look much better.

Highlighting of Played Quizzes. No more taking the same quiz twice and getting no credit for it.

Extended Statistics. Gold members will have access to refined statistics online and via email.

Gold Member Control Panel. Each Gold member will have a panel of options, which will allow them to set site preferences and customize their experience on 123facts.com.

Recognition. Gold members will get a cute logo next to their name everywhere on the site.
New features will constantly be added to the Gold members program.
As ads have become very annoying and costs of maintaining a quality site are rising, this new approach will offer an alternative to adding more and more banners.
Any thoughts?
-esprit