Last I heard wiping things more than once is just a time waster, has anyone actually done some scientific research on this yet? Here is what cvpcs had to say about wiping last June: Still Loading ... ? blog:2011-06-05:time_to_wipe_data:cache
dunno but there were some issues with htc thunderbolt at least, rumored, dunno how real they were. anyway, force of habit, and dalvik wipes take like a second, so i just do it a few times.