I love Nextend Facebook Connect - it is a truly amazing plugin. However, I noticed it has been flooding my site's mySQL database, in particular the wp_options table with thousands of "_site_transient_" entries. This slows down the site significantly, and ultimately led to the site consistently timing out.
This can be fixed with a database query:
DELETE FROM wp_options WHERE option_name like '_site_transient_%'
But, I would hate to have to do this periodically to keep using this plugin. Would love it if you guys could look into this.