its not digging the things you are interested that is the problem its when someone posts a live link to digg or live link to their dig button and openly asks people to digg it, all digg exchanges should be done through PM, ive had a digg account banned in the past too because i posted a live link and didnt think oopps.
Remember there couldbe/are Digg employee's surfing around webmaster forums to stop these exchanges so PM is the best option.