Is Vacuuming Bad For Your Carpet?

My husband recently took our sons on a father/son outing. They ended up at a department store...in the power tool section. On their way back through the store they happened across the vacuum cleaners. The sales associate was very surprised when my sons started naming the different brands of vacuum cleaners. We like vacuum cleaners in our house. But what about the people who say that vacuuming is bad for your carpet? Truth or cleaning myth...we'll sort it out.