Jeremy Cole recently blogged about the feature SET GLOBAL sql_log_bin. In his blog post, Jeremy suggested that there is no strong use-case for this feature, and that it is too easy to run accidentally (i.e. SET GLOBAL instead of SET [SESSION]). The result of this incorrect usage is that slaves will drift out of sync from masters.
We discussed Jeremy's request in the MySQL team, and we agree that the syntax should produce an error in MySQL 5.7. However, we have not yet determined which steps should be taken for MySQL 5.5 and MySQL 5.6. The two proposals we would like to float are: