Nothing happens (officially).
According to the ITTF Rules:
2.11 A Game
A game shall be won by the player or pair first scoring 11 points unless both players or pairs score 10 points, when the game shall be won by the first player or pair subsequently gaining a lead of 2 points.
In unofficial matches there may be a so-called mercy rule (or skunk rule), which may end a game after a 7-0 lead or other standings. Since no official rule about this exists any longer the requirements may vary.
The USATT also has some extra basement rules (they're not real rules!) which still include a skunk rule:
12.1 Scores of 7-0, 11-1, 15-2, and 21-3 are game winning "skunks". As if being "skunked" isn't bad enough, the skunkee may also be required to perform push ups or drink two beers.
12.2 The loser of a game is required to drink a beer. In the event of a "skunk" the loser must drink two beers.