Yes, blowing in the cart. was so common that Nintendo supplied us with orange stickers warning people not to blow in the cart. that we had to put on every deck we repaired. They also sold cleaning kits for the games, but if the kid had been blowing too long the corrosion would be too bad. In that case the game had to come apart and be cleaned with chrome polish.
I used to get so incensed with my friends for blowing on the cartridges. Try though I might, I simply could not convince them that 1) re-seating the cartridge was what made their motion effective, and 2) they were ruining their cartridges at the same time. And of course having a number of gamer magazines at the time recommend the blowing technique didn't help. I remember similar problems with the Atari 2600, though not as prevalent, and with the dust covers built into those cartridges you couldn't blow on them so re-seating was the only real option available (excluding, of course, third party cartridges which did not have covers over the boards.)
