The rights to your work are yours, and if someone copies your work and posts it as their own somewhere you can report them. If someone steals your work and gets reported they may have their account (on HubPages or elsewhere, as well as with Google) closed.
Original work gets stolen all the time. Catching someone who has stolen your work can be tricky; although some types of Hubs/articles are more likely to be stolen than others.
Sometimes HubPages (or any writing) will catch it when someone posts your article online because you'll see, "duplicate content" (which may nor may not mean someone else posted the same material, but which can also mean you have it somewhere else online under your own or a different name). Sometimes you can find your material somewhere else online if you put the first couple (or so)_ of lines in quotes and search Google for that.
With online stuff there's always the chance someone will copy it. They can also copy it, run it through an "article spinning" program and post it with words slightly altered. They can also steal your work, post it under one name, get caught, and then just open an account somewhere in another name and start stealing again.
It's a problem. Writing sites try to do what they can. Writers are pretty much responsible for finding a lot of their own stolen material. People keep trying to find new ways to prevent stealing, but other people keep figuring new ways to steal it. Material that ranks high on Google pages is at higher risk, so if you write something like, "My horrible childhood" it's not as likely to be stolen (or earn money for you either).
I don't put any writing I care a whole lot about online (but it's still aggravating to discover someone has stolen your work). If you have Hubs that earn you anything you may notice your earnings or the Hub's score drops drastically. That's because it's no longer unique online.
I'd suggest you learn what type of Hubs are most likely to be copied and develop a system for checking online (particularly if you notice a major drop in score or earnings); but also that you not post anything that, stolen, would be really important to you. The stuff with traffic/earnings isn't good; but it isn't the end of the world if someone steals it.
The way I see it, there are things to gained/ learned from online writing; so you have to weigh the benefits against the whole potential theft thing.