I think tattoos should be covered up in the work place. The reason being that you don't want to offend your coworkers/clients with your tats. Since there's really no way you can say what kind of tattoo should be allowed, its best to just put them in the same category and call it a day.
For example, some people have military tattoos on their bodies. This could upset some people who don't agree with the military. Some have tats of women and men performing extreme sex practices. This could upset children. And so forth and so forth. What you think "isn't so bad or cool" may not be the same for eveyone else. Its the same with clothing. The logos you have on your clothing should be in compliance with the company's image.
But then at the same time, as someone said, there are those who have tattoos as part of their religion so....that's an iffy one.
