5. Kim Kardashian and Nick Cannon

When? 2006
Why? Kim met Nick through her then-BFF Paris Hilton.
How Long? 4 months. He told Howard Stern that the relationship ended because of Kim's sex tape. "This was my issue. We talked about this tape…And she told me there was no tape. If she might have been honest with me I might have tried to hold her down and be like 'That was before me' because she is a great girl," he said.