Scott Stroz Asks: "What is Considered Premature Optimization?"

Scott just posed an interesting question on his blog. I think we all agree that focusing too much on performance upfront to the detriment of maintainability or functionality is not usually a good idea. But equally, none of us would write an app that deliberately included every bean being created in the request scope and n+1 queries. So, what is just common sense or best practices and what would come under premature optimization?

To me it is more a state of mind or focus than anything else, but I'd love to see people post comments on Scotts blog about what they do and don't generally consider "best practices" vs. PO.

Thoughts?!