Is a tie appropriate with a polo shirt?

[Colin]

Seriously?!?!?

my answer would be NO!!. Polo shirts are made of stretchier, more breathable material for casual comfort. It's a whole different level of comfort and formality. If one of my co-workers came into a meeting with a polo shirt and a tie on I would likely beat him with a file folder until the tie was removed. This also applies to golf shirts and rugby shirts, sweat pants with dress shoes, white sport socks with dress shoes, socks with sandals, and people still wearing ripped concert shirts and jeans in the 30's+.

Ties are for dress shirts and usually indicate some form of formality (usually business formal).
Polo and golf shirts are most recently used for casual Fridays or business casual (it's a step up for a t shirt).