bencozzy and Toddrtrex were the only ones that actually specified what kind of carpet anemone they were talking about. When someone says "carpet anemone," they are referring to three different species of the genus Stichodactyla. S. Gigantea, S. Mertensii and S. Haddoni are three carpet anemones so when you use the term "carpet," you could be referring to anyone of those species causing confusion.
jdog6973, when people say "keeping a carpet anemone is difficult" they are probably referring either to S. Gigantea or S. Haddoni since those are the most commonly sold carpets. S. Mertensii is not as frequently sold in the hobby. In my experience, I have kept two S. Haddoni and one S. Gigantea. I have found that under the adequate condtions, keeping a Haddoni is relatively easy. That's not to say that they are easy because what might be common sense to an experienced anemone keeper might not be to an average aquarist. Most anemone keepers in general do not know how to care for one long term which is why statistically 1 out of every 32 anemones kept in captivity only lives passed two years.
However, when I attempted to keep a S. Gigantea, I only managed to keep it alive for about two weeks. These carpet anemones are INCREDIBLY difficult to care for. The chances of having success with this species of carpet is lower than 10% and that's no joke. I would definately avoid even trying S. Gigantea unless you have been keeping anemones for a while.
If it were me, I would do more research on carpet anemones before you buy one. Usually when members here ask questions such as "how hard are they to keep alive," they usually do not know what they are getting into. There are plenty of threads in the "anemones and clownfish" forum to look through that can provide you some information.