Impressive that they racked up 1.2 million subscribers already, of which roughly 0.5 million are active, in the short space of 5 and half months. Compare this to Virgin Mobiles record over the last 3 years, and it looks even better. On the other hand, they've already lost 0.7 million subscribers (no longer active), more than half their total subscriber base. Something's definitely wrong.
These prepaid ARPU figures are extremely low. I think Vodacom's and MTN's prepaid ARPU is between R60 and R90 if I recall correctly, and Contract ARPU is between R300 and R350.
All the above indicates to me that most people are still testing the waters with 8.ta. Nobody really trusts them, but with good offers, people are willing to give it a go. Sounds like alot of people did give it a go, but then left, for some reason. Perhaps most of these people are using the SIM cards for the free calls to a single specified Telkom number, or perhaps 8.ta hasn't managed to shake off the perception that consumers have of their parent company.