1) The "third party cookies block" championed by Safari for one.
2) Refusing to let the publishers get user info without the user opting in first (there was big hoopla about that from the publisher's end):
http://counternotions.com/2011/02/16/stores/
"As part of a more stringent ruleset regarding customer privacy, Apple has reportedly started rejecting apps which access UDIDs in a practice that will become de rigueur for all review teams".
1) The "third party cookies block" championed by Safari for one.
2) Refusing to let the publishers get user info without the user opting in first (there was big hoopla about that from the publisher's end):
http://counternotions.com/2011/02/16/stores/