This explains the "leaks" pretty well:

"Sources close to both Obama and Clinton told ABC News that the New York senator is highly unlikely to allow her name to be formally submitted for a roll-call vote on the convention floor. The Obama campaign wants to avoid such a vote, since it would underscore the party's splits and remind voters of the divisive primary campaign between the two Democrats.

The refusal to publicly announce her intentions is widely seen as a bargaining chip Clinton is holding on to as party officials negotiate logistics regarding her convention speech and other activities, according to several Democrats who are closely involved in the matter. Read more…