Yep, for me it happened for all my contacts (Facebook, GTalk, Skype and AIM) too.

Though it happened only once (when I rebooted and got online for the first time after installing the app).

Tested it again for:
1. Reboot and went online - did not receive those bulk notifications.
2. Went offline and online - did not receive bulk notifications.
3. Disabled an Account and re-enabled - did not receive bulk notifications.

Not sure how you get the presence change but seems the notifications were for initial presence change (no presence to offline/online). If this can be handled by some post install script which suppresses the notifications but just gets initial presence, then there won't be these bulk notifications. I may be completely out of context here but just a thought.