Hi Simon,
If you are playing a Match Play game then the opponent automatically forfeits after disconnecting from the match 3 times. Match play is a "versus" mode and wins/losses are kept, so we will penalize the player for disconnecting on you.
Ranked Stroke Play is not a "versus" mode and no win/loss tallies are kept. Ranked Stroke Play (even in a group) is just pitting the the player(s) against the course instead of against each other. "Ranked" just means that the stats are kept and your scoring average is adjusted when the round is posted.
Other than providing an inconvenience nothing is gained or lost by you if someone else disconnects on you during a ranked stroke play game. You always have the option to finish out the round yourself in single player, so your time spent is not wasted.
We are working on a reputation tracking option that will help players avoid those who like to disconnect on a frequent basis. With its implementation you'll know what to expect from a player before you tee off and you will be able to make better decisions about whom you play with.