As it is written for v2.0 of Last.FM's scrobbling API, YAMS does not store your username or password locally, but opts to use a cookie instead. Similar to other scrobblers, YAMS can save failed scrobbles and upload them at a later date. It also offers a decent amount of configuration options for when/how a scrobble should be made (including ignoring duplicate scrobbles when a track is played multiple times in a row).