The ISS is an international version of MIR and SKYLAB. Why is it up there? Well, for once it is a place to prove, develop and learn about long term stays in space, they have whole fricken sections of the station devoted to experiments, it will also provide a lot of data and lessons for any future manned space station, hopefully a permanently manned one.
WTF you people want? DS9?
Im truly amazed how many countries are participating, that itself is a great step foward.
As for having tourists up there... why not? Only a millionaire would be able to go up there at these stages, and even if some lame bellybutton hollywood actor with too much money on his hands goes up there, he may end up giving donations to NASA or aid the space program... being in space is a deep experience. Tourists being a danger? You'd think someone with the money to pay his way up there would have the brains to keep his hand to himself.
Anyway, ISS is up there, its good, lets hope it helps us make a base on the moon in the future, its about fricken time we got up there!!!