I've overdone it by a mile once or twice when I was new to the game.
Less is almost always more, i've learned. An underseasoned but well cooked rib is still delicious, an overseasoned one makes you want to eat something else.
If you have a sweet rub, you have to put a LOT on to ruin them, but if you have more of a spicy/hot rub, too much is awful.
Cat Daddy's BBQ : 22.5 WSM / PBC / Akorn / Weber OTG 22.5 Cajun Bandit / Smokey Joe Gold