I brought Scotch back from my study abroad year in the UK...just one liter, stuffed into my checked bag. No one inspected me and I never had to talk to anyone about it.

I was mildly concerned that someone would take it since I was only 19. Thankfully it wasn't an issue.

Of course, this was many years pre-9/11 and well before anything like Global Entry that would record you as a smuggler for life. These days, I'm pretty diligent about reporting everything even though I'm never bringing more than 2 liters back (can't fit any more than that into my checked luggage!)