When Optus launched its prepaid 3G broadband service back in August, we noted that there was a nasty catch: usage was charged in 10MB blocks. Now Dan Warne at APC reports a new and nastier twist: the value of recharges on the service has just been dramatically reduced, with (for instance) $30 now getting 1GB of downloads rather than 2GB. Telstra's rival prepaid service is the main alternative, but also comes with a sting due to its 30-day expiry rules. The moral? As ever, choose carefully before going prepaid.