Tell a Friend Plugins Vulnerable?

I just installed the Tell A Friend Popup Form plugin on a DP site. See the plugin site here:

https://www.gopiplus.com/work/2012/05/21/wordpress-plugin-wp-tell-a-friend-popup-form/#.Ugkhxn_pydw

Has anybody experienced bad spamming or worse with these plugins?

Yesterday I installed the Stop Spammers plugin at Richard Bonk’s recommendation and the daily dribble of 1 or 2 spam registrations stopped. It works.

Wordfence is also installed with the usual offending countries blocked.

Will the Stop Spammers plugin protect Tell A Friend? Or are these type of plugins risky?