While it may seem picky to argue over not quite a penny per page view, the person doing this is taking page views away from you, which however small it may be does affect your bottom line.
More importantly, if you write for places like Triond, Associated Content or Suite 101 it affects the revenue of the company publishing your content as well. However, since your success ties in to their success however small your success might be in their overall scheme, you can enlist them as a slightly more powerful ally when you discover this has been done. Take my word for it, you will.
Most people who cut and paste content are not doing so deliberately to rip you off. Sometimes they might be doing it out of concern for their readers, many of whom may not like having to leave the site they are currently on. Personally, I do not like doing it if I am on a message board forum, but bloggers copying articles merely to find content for their blogs either should content the site the original piece is hosted on or merely use a paragraph or two to tease the reader into reading the original article and link back to it. Such usage falls under “fair use” rules and will not cause a problem.
Once you find someone has copied one of your articles, what should you do? Before calling out the big guns, check what they did carefully. Odds are they are attributing it to you, but they simply misunderstood how they were allowed to use the piece. Contact them as discreetly as possible and explain what you would like them to do. Most people will not give you a hard time about it. If however, the person is reluctant or hostile, then you may wish to contract the administrators of the site you write for, if you write for someone else. Those striking out on their own many have to contact a lawyer who specializes in copyright or intellectual property law or simply drop the matter.
If however, you are writing under contract for someone else they have a little more reason to fight for the person to change it to what they want, and more than likely they have a legal department who can add a little extra weight to your claim. If it is that important to you not to have your work used where you cannot make money off of it, contact them first. They will likely be able to resolve it faster than you would alone and let's face it, you write for these places because you personally did not want to deal with the legal hassles and more importantly, things like search engine optimization.