Glo has been giving out free airtime to glo subscribers since yesterday on their Facebook fan page. I don't know the exact amount of these cards because, I have never won. The policy on winning the free cards is fasted FINGER first. They are loading the cards randomly. Try, you might be so lucky. Good luck.
Remember, it is fasted finger first.

Below are the post I copied from glo FB fan page.

Yesterday:
1. Glo fans on facebook keep checking on the Gloworld page today and you could be amongst the lucky winners of some free recharge credit if you are the fastest fingers.
http://www.facebook.com/GloWorld/posts/10150182944878435

2. The surprise of free airtime recharge will come any moment now so keep checking your GloWorld on facebook
http://www.facebook.com/GloWorld/posts/10150183031768435

Today:
. The surprise of free airtime recharge will continue to come so keep checking your GloWorld on facebook.
http://www.facebook.com/GloWorld/posts/10150183858918435

I just hope I will win one as long the offer lasts.

nice