GUIDs are HUGE and have a significant impact on performance. Go read Kimberly Tripp's blog post referenced in the article. She does the math for you.

In almost all the cases that I see GUIDs, they were totally unnecessary for the design. Even the developer who designed them could not give a reason why they needed to be GUIDs. A row unique across the entire universe? Really?

I'm not saying there are no cases...just that in most cases they negatively impact performance with little business or logic gain for that price. All design decisions come down to cost, benefit and risk.