This is not legal advice.Just my thoughts. I haven't done any contemporary research to answer your question. I'm just going by my own fallible memory.
The law that protects your writings (and, for example, photographs) when you put them on the web is the same law that protects them otherwise: the Copyright Act (Digital Millenium Copyright Act, or DMCA). What those Creative Commons licenses do--it seems to me--is essentially waive a portion of the rights given to you by DMCA as the owner of creative content. The more permissive the Creative Commons license, the more rights you waive. (The most liberal of these licenses essentially waives all your copyright protections, as you've allowed the copyright infringer to even make commercial use of your content. I've read of authors using the most liberal Creative Commons license and then seeing someone else charging for the work the author put on the web intending it to be freely used.)
If someone uses your material in a way that you think wasn't allowed under the Creative Commons license, you can send them a "take down notice" as described in the DMCA. This notice, as the name implies, demands that they pull your, content off their websites. You don't need an attorney to prepare and send this notice, but you do have to include a half dozen specific items to make the demand a legal one. No big deal; you can email it but you do have to track down the owner of the website(s) listed by their ISP.
But what if they ignore you or you can't find them through their ISP and leave your content on the web? Or if they've distributed your writing to others on the web and you have to play whack-a-mole, sending out take down notices to multiplying website owners?
The only thing you can do is to sue them under DMCA for damages. IF the judge finds that there is a violation of the DMCA, then you can ask for what are called "statutory damages." This means that you can get a minimum of $750 up to $30,000 (I think that's accurate) without proving you had any actual monetary damages. It's possible you could get an attorney to do this for you on contingency, as I think DMCA allows you to request attorney's fees.
HOWEVER, if the judge believes that the Creative Commons license created a contract between you and the person who stole your writing that's been broken, you are pretty much screwed. This is because, unlike the DMCA, a regular contract requires you to assert monetary damages. What sucks is that it would be next to impossible to prove any monetary damages since you've already agreed to let others use your content for free (at least in some ways) by creating a Creative Commons license. Also, I suppose it's possible that the judge could find that you had violated some term in the Creative Commons license and, in a nightmarish albeit unlikely scenario, you would be liable to them for damages. Contract law is very tricky.
In short, AS I SEE IT, you have nothing to gain and much to lose by using these Creative Commons licenses. Your rights are still only enforced by the DMCA, but you've waived some of those rights by subscribing to the Creative Commons license. (Notice that I kept referring to the DMCA as your only recourse whether you have a Creative Commons license or not.)
What to do? AGAIN, THIS IS NOT LEGAL ADVICE, but it is very simple to put a copyright notice on your web content. I don't want to tell you how, but Google.