I have mixed feelings on this.
Same as D0oinMeCleanin I download legally where possible. (PC games, PSN, mp3 sites, etc) but the movie/TV industry is really behind on the technology. They could dramatically decrease the amount of piracy by taking the cues from other industries.
Services like Netflix and Lovefilm Online were long overdue, and still need work.
Plus, it is much more convenient to have access to digital/online versions of different media. Rather than needing a hard copy.
I remember years and years ago, there used to be a website where you could download free mp3's, the vast majority of music on that site was uploaded by the bands themselves. But when Napster got shut down the owners of this other site shut down as they were not able to guarantee that every bit of music uploaded was uploaded with the permission of the copyright owner. This was before streaming was a real possibility. Luckily with the advent of streaming it became easier to find new music without having to take a gamble on buying CD's. Why the movie/TV industry isn't taking advantage of this I do not know!
It is good to be able to sample something before buying. It means you are more likely to try something you wouldn't normally. It seems especially beneficial to smaller, independent producers who don't have the budgets to push their products.
I have, in the past, downloaded things I wasn't 100% sure I'd like, and then gone on to buy them. If I hadn't downloaded them I definitely wouldn't have bought them. This is also one of the problems with the figures put out about how much is lost through piracy. It assumes that every download is a lost sale. When they can't guarantee that. It definitely doesn't take into account the fact that in some situations a download can gain them a sale that they wouldn't have had otherwise.
One last thing, it really isn't theft. To steal something you have to remove it. Copying isn't stealing. This isn't to say that it is right or legal though.
Copyright theft is a totally wrong description, as that implies that you are taking it's copyright. Which you aren't. The closest you could come to stealing copyright is to claim something is created by you, and profit from it.