That's up for debate. Generally the MPAA and RIAA have been waging war against these types of sites unsuccessfully. The problem is that every country has different laws on copyright, and technically these sites aren't hosting any of the illegal material, just giving 'directions' on where to find it. The question has gotten to the point now where it doesn't really matter what the courts decide, the internet is going to do what the internet does. It's more important now to figure out how to give users added value in order to promote whatever digital content you are selling so that people are less tempted to pirate it.
I would like to start a search engine of this kind and I don't think this is illegal because I don't host pirated music, videos and games!
I believe they are legal and in reality you are just searching files on a company's website. It is certainly not like searching through torrents for example. RapidShare is a paid service and they hold the responsibility of hosting your files.
they are not legal, but made using legal ways. the site admins allow other people/users to post their uploads and share it with others. This was the admin cant b blamed. The uploaders upload to file-hosting sites so the file hosts can b blamed, but then file hosts cant keep track of every single user uploads. So the filehost cant b blamed... so an illegal thing is made legal shareing this way.