I was playing $1/$2 nl at Stones today and the small blind tossed in a $5 chip to raise to $6 after a limper had joined the pot.
The dealer said it wasn't a raise since it wasn't announced. He called over the floor who confirmed that when a large chip goes in unannounced it is just a call.
Everyone knows how this applies when there is just a single chip (the one chip rule). In this case there were 2 chips so the small blind was frustrated.
I guess it is something to think about when online players venture out into brick and mortar games.