PHP Fatal error: Uncaught exception

Hi,

one of the subsite blogs of our WP network is using the Google+ plugin and we noticed it causes a lot of fatal error in our php logs as follows:

[15-Sep-2013 23:20:34] PHP Fatal error: Uncaught exception 'Google_ServiceException' with message 'Error calling GET https://www.googleapis.com/plus/v1/people/https%3A%2F%2Fplus.google.com%2Fu%2F0%2F109390647791318749471/activities/public?maxResults=5: (403) Daily Limit for Unauthenticated Use Exceeded. Continued use requires signup.' in /XXXX/wordpress/public_html/wp-content/plugins/wpmu-dev-plusone/lib/external/google/io/Google_REST.php:67

Is it a normal behaviour of the plugin ?

thanks