I'm always cautious about these things. Creating a Knol page is working on something that you do not have complete control over. I have no doubt that Google will delete Knols anytime they feel one is inappropriate.

It is, of course, entirely possible that people will make money from their Knol pages. There are many people already making money from sites on Blogger and pages on sites such as Squidoo or HubPages. Some even do pretty well.

It's a cheap way of creating web pages, which appeals to many a tight-budgeted marketer. And so many pages do get some pretty good traffic that this can be appealing.

But what you give up is control.

Don't assume that just because you have legitimate information to share that someone won't try to get you removed from a particular service. It has happened to many on Blogger, for example, and not just to spammy pages. It is possible for legitimate content to be flagged by competitors. Creating pages on a service you aren't paying for means that you risk the account being deleted, sometimes with poor warning.

On the plus side, creating a Knol, Squidoo Lens or what have you means that you are listed on a site that may get traffic with less of your own effort. There can be a benefit to that, especially for keywords that you are having trouble ranking for anyhow, even if the links to your own sites are No Follow.

The key to these is to add to your own image as an expert on your topic. Create a good page and be sure to have links to relevant pages of your own. Not to excess, as the page you are creating should stand mostly on its own. But as a reference for more information or details that are related to the topic at hand, the occasional link to your own site can help to drive traffic.

Do it too much and your page will look more like spam.

Overall, there's nothing wrong with creating pages on services such as these, so long as you build a solid core business that you have more control over. It's rather like article submission in some ways. You're spreading content out in the hopes of bringing in more traffic and income. So long as you are not relying on any one page or group of pages for your livelihood, you'll probably do all right.