They sure can. I work for one of the largest internet companies in the world, so I can speak to that area.
We have a very relaxed corporate dress code, although not as relaxed as Intel's Hawaiian shirts. Jeans Jeans and Jeans. I couldn't imagine our creative environment surviving with out it. Suits? Slacks? It doesn't fit and doesn't work.
However. Sometimes the relaxed code can go to far. Have you seen this picture of <a href="http://graphics8.nytimes.com/images/2006/11/09/business/10deal1.300.jpg" target="_Blank">Mark Zuckerberg</a>?
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