I'm not sure how Baruch posted as a Guest. I deleted it as spam.
Basically, once the ACD subsystem selects an Agent to receive a call, that call will show as an Abandon for that agent if the caller hangs up before the agent answers. If you have your agents set to auo-answer ACD interactions, you should not be seeing abandons since the call doesn't spend time in Alerting. Theoretically, it could happen, I guess, but only on very rare occasions when a caller disconnects during the split second between the ACD subsystem selecting an agent and the call connecting on the agent's phone. That could potentially come into play as well when you have a customization in the CustomACDPreAlert handler that delays getting the call to an agent.
Anyway, you usually only see Abandons on the User Productivity reports when the agents are not set to auto-answer, to the best of my knowledge. On the User Productivity Summary, for example, you can see a column for Offered (how many calls were sent to that agent), Answered (how many actually went Connected for that agent), Abandoned (how many went to Alerting but never Connected), and Flow Outs (grabbed by a Supervisor, for example, while still Alerting).
Another potential source of Abandons on that report would be an agent seeing a call in Alerting and clicking the Disconnect button instead of picking up the call.