Gravatar's business model is collecting user data from images (Gravatars) embedded in other websites. [1}.

We have already disabled Gravatar in JIRA (OTHER-265) and people have noted that the current setup of silently using Gravatar without any possibility of opting out is not ideal ([2, MBS-8685).

Another, more elegant solution might be caching Gravatars server-side, the way Discourse seems to handle it.