There is a proposal to change the default behaviour of git push on the Git mailing list. The goal of this message is to encourage you to discuss it before it happens (or the change is aborted, depending on the outcome of the discussion).
In the current setting (i.e. push.default=matching), git push without argument will push all branches that exist locally and remotely with the same name. This is usually appropriate when a developer pushes to his own public repository, but may be confusing if not dangerous when using a shared repository. The proposal is to change the default to 'upstream', i.e. push only the current branch, and push it to the branch git pull would pull from. Another candidate is 'current'; this pushes only the current branch to the remote branch of the same name.
For more details on the behavior of Git with these values, read the documentation about push.default in 'man git-config'.
You may be negatively affected when such a change happens if you do not see anything in the output from git config push.default and if you rely on the default that pushes all your matching branches. On the other hand, you may want to see the default behaviour to change, especially if you are using shared repositories. In either case, please join the discussion to give us more data point and help us decide the future of Git. Also, if you think your friends and colleagues will be affected by this change, either positively or negatively, please tell them about this discussion.
What has been discussed so far can be seen in this thread: