WordPress.org

Where is data stored?

A table, wp_social_media_email_alerts, is created (the wp_ prefix may actually vary based on your configuration). This table stores the visits that match the rules you specified. The records in this table are deleted once they no longer match a rule or have expired so the table shouldn't get too large.

Does this plugin work with caching plugins?

Yes. Simply specify on the admin page that you are using WP-Cache or WP Super Cache. Should work with other caching plugins too.

Does this alert system work only for social media sites?

No. You can specify any referral domain of your choosing. Social media sites are simply what prompted the creation of this plugin.

I like this plugin, do you have others?

I sure do!

Real-Time Find and Replace Set up find and replace rules that are executed AFTER a page is generated by WordPress, but BEFORE it is sent to a user's browser. http://wordpress.org/extend/plugins/real-time-find-and-replace/

RSS Includes Pages Modifies RSS feeds so that they include pages and not just posts. http://wordpress.org/extend/plugins/rss-includes-pages/