Natrlhi is spot on with all the TSA stuff, though most of my flight experiences have been international and the rules vary wildly in different places. The valet thing is not in practice in most places.
In the US usually there are baskets they have at various places in the airports, including at the gates, where people are supposed to place their questionably sized luggage to make sure it fits. Oversized luggage has never been an issue in my experience though. Nor has there ever not been enough room in the compartments for luggage. My angst is with people failing to be able to identify what's theirs and what's not theirs.
Never whistle while you're pissing.