Well, I'm not sure I'd consider it writing, per se. The Squidoo page is more like assembling a collection of links, articles, affiliate links, eBay auctions, and so forth on a particular, narrow topic.
Squidoo is like blogging. No--wait. It's like About.com. Well, sort of. It's more like Associated Content. Um, no--it's like Helium. Well--it's like all of those.
Look at http://www.squidoo.com/giftedkids/ to see an example of a Squidoo "lens." A lens is a specific topic you choose. You use the Squidoo publishing process, then, to add "modules" to your particular Squidoo lens. For instance, you can have blog text boxes, add links to eBay auctions, links to books on Amazon.com, RSS feeds, and more.
With Squidoo, you can choose to be paid cash for any revenue your site generates. The content can remain, and there are no requirements for refreshing the page. In theory, one could spend 2 hours creating a lens, and then sit back while it generates $.10 per month in perpetuity.
Users are not limited in the number of lenses they can create. Last May, Squidoo was reporting that their top lens creators were earning $30 per month (or so) from lenses. Again--if you're blogging on your own, you can earn more via Adsense (more on blogging later), but the Squidoo lens could involve an initial time investment of 2 hours, then a once-a-week 10 minutes brush up. $30 per month for 40 minutes per month isn't bad, if you can get there. Multiply that times 10 lenses, and you have a decent little deal. For $.10 per month? Not such a great time/revenue ratio.
On the other hand, for writers working to promote articles on other sites, such as Associated Content, Squidoo might be worth the time investment. Associated Content writers could create various lenses, link to their own articles, and help generate higher Google rankings AND additional readers. So as a tool to promote content, Squidoo might be worth it. As a moneymaker--that remains to be seen. As my Squidoo lens picks up more readership over time, I will report back.