Domain tasting is the disreputable practice of registering lots of domains, seeing how much traffic they get, and then using the five day Add Grace Period to refund the 99.9% of them that aren’t worth paying for. A related abuse is front running, registrars speculatively grabbing domains that people inquire about to prevent them from using a different registrar.
In January, the ICANN board voted to make their 20 cent per domain fee non-refundable, effective probably in the next budget year which would be 2009. That would deter the highest volume tasters but as other people have pointed out, it wouldn’t have much effect against front running if the 20 cent fee might lock in a $30 registration and a $100 hosting package.
Further information at: http://www.circleid.com/posts/84217_icann_gnso_kill_domain_tasting/