Uwe Brauer wrote:
- How can I find out, whether the same user has various accounts and give the false impression that many users contribute. I presume it must be via the IP (also in case of multi user machines that might be misleading).
You cannot find this out with technical means. There is a tool called CheckUser that tries to do this, see http://meta.wikimedia.org/wiki/CheckUser
But access to CheckUser is only available to highly trusted people, and it never gives 100% accuracy anyway. Many people can use the same IP address, and one person can use many IP addresses, especially through anonymous proxies.
There are people with split personalities that are experts in Greek archaeology when they are Mr Hyde, and experts in hip hop music when they are Dr Jekyll. In order to maintain the illusion, such Wikipedia sock puppets can sometimes vote against each other in Wikipedia opinion polls.
There are also people who have nothing else to do, but are awake 18 hours a day, working 9 hours as Mr Hyde and 9 hours as Dr Jekyll, only leaving 6 hours for sleep. Don't get surprised!
Note that this is not forbidden. As long as Mr Hyde and Dr Jekyll both contribute to articles, this is fine. It only becomes a problem when they enter into conflict with other people.
The only 100% working solution is to get in touch with the people in real life. If they turn up at a meeting or a conference, they can prove whether they are one person or two different ones. If only Mr Hyde shows up, but never Dr Jekyll, you cannot know. Telephone and e-mail are not good enough. Unless you meet them in person, you always have to be in doubt.
You can get quite certain in cases where two characters are more famous, covered by media, etc. For example, I have never met Nelson Mandela or George Bush, but I'm quite sure they are not the same person. If they were indeed the same person, and tried to cover up this secret fact, the effort of this cover-up would be far greater than the benefit. This is not a proof, but an indication based on mathematics and probability. And that's also what you can get from CheckUser. Sometimes that's good enough.