Some new users don't know how to edit their own answers, so they post their edits as a second answer to the same question - as people do in forums.
I suggest that we limit the number of answers per question to only one answer for users with low reputation (e.g. less than 50).
For example see my question Could not find adb.exe - after upgrade to Android SDK 2.3, it has five answers. And four of them are from users with reputation 1 that have posted two answers.