WordPress.com added two new email notifications, one for likes and one for subscriptions.
"Post authors will receive an email notification from WordPress.com, telling them which post was liked and who it was. And blog owners will receive an email when someone new subscribes to their blog. This gives instant feedback every time your post or blog gets some positive attention."
"If email notifications aren't for you, no problem. You can turn these notifications off by going to Dashboard?Settings?Discussion and deactivating the appropriate checkbox under "Email me whenever".
For particularly active blog, some features are by default in off mode, so you wouldn't be annoyed. You can turn them on if you wish as described above," stated WordPress.
More details can be found in the support page for email notifications.