Suppose there is a popular website in a .com extension. How would it affect the traffic, search-engine rank of my website if I registered the same name of the popular website, except in a different extension -- such as .us

This is assuming there would be no trademark violation in doing so, and that the new site would redirect to my own website (which deals with a very similar subject matter). Another option might be to set up a mini site and a create some links to my own website.

Any thoughts on the effect this would have?