Keep in mind the delivery date on the Apple website when we pre-ordered was "Delivers *by* June 19th". Not "on" June 19th", but "by" June 19th. It's a small game of semantics, but it does have a different meaning.
After the disappointing announcements about both MMS and tethering being delayed by AT&T (and seeing that cryptic delivery promise from Apple) I fully expected Apple pre-orders to arrive early in order to:
1) Generate additional buzz for the product when some of them showed up early
2) Further distance Apple from AT&T in consumer's minds, so that the next time a big upgrade comes around people are driven to purchase through Apple channels.
3) Give a big "F U" to AT&T over the MMS and tethering issues (and their crappy network).