DRM stands for Digital Rights Management and it is a way of limiting access to multiple devices for software, music, eBooks, and other digital goods. If DRM is enabled on a digital item that is sold to a customer, there are restrictions on where they can copy it and who they can give it to. While the schemes have varied throughout the years, the consensus from consumers of digital goods seems to be unanimous: DRM is hated by buyers of MP3s, hated by gamers, and it is most definitely hated by eBook readers.
Large corporations tend to make the argument that DRM prevents piracy. This is nonsense, because you can log onto any torrent site and find software, eBooks, and anything else that has been stripped of its DRM. Hackers have been designing cracks for every piece of software ever since the Commodore 64 came around. The DRM scheme is simply a way for honest people (like your Grandmother who just got a Kindle) to have to either pay for multiple copies of the same product or go through the technical hassle of validation when they change devices.
Another flaw is that DRM assumes people are criminals when they buy a digital product by putting pre-emptive restrictions on it. Do you really have that much disdain for your readers? If your own Grandmother loaned a print book to her neighbor, would that make her a criminal? The suits at the RIAA seem to think so. However, they have a strange view of what "theft" constitutes. If someone comes into your house and steals your wallet, that is undoubtedly theft, because you lose money and property. However, if someone downloads a copy of your eBook without paying, do you really lose money or property? It's an argument that is worth contemplating. However, to paraphrase David Gaughran, for indie authors the enemy is obscurity, not piracy.
Additionally, in places like Thailand, piracy is rampant and open. You can walk down the street or even go to malls where DVDs that come in little plastic jackets are being sold for approximately 2 to 3 dollars. This is not because Thai people are bad, it is because the country has a lower GDP than its Western cousins and cannot afford the 10-20 dollars that DVD distributors like to charge. If anything, you should explore a pricing strategy that is proportional to GDP. In Thailand, the Asiabooks eBook store is new, and you can explore different eBook outlets in countries around the world to try various prices. Hopefully, more will come online in the future (particularly in countries with huge amounts of English-language speakers like India and the Philippines). As indie authors, it is important to not think like the corporate stiff who only worries about return on investment for shareholders, you need to think like the small businessman (or businesswoman of course) that is 100% dedicated to customer satisfaction.
Smashwords is philosophically opposed to DRM and does not allow it for any of the eBooks sold on their website. When you upload to the Amazon.com Kindle store and Barnes & Noble NOOK, you have the option to use or not use DRM. You should strongly consider not utilizing DRM in your eBooks, as a courtesy to your readers. Instead of creating unnecessary hassles for the customer and fretting about someone downloading a torrent of your eBook, which will happen whether or not you use DRM, you should focus on impressing your customer and using a pricing strategy that maximizes distribution. Try spending your energy on what's really important and challenging, which is writing stories that readers enjoy.