"... each ticket buyer was asked to list employer and job for federal election reports because it was a political event."
Why does anyone have to fill out govt forms to attend a Springsteen concert? or even a political event?
Because it was a political activity where the cost of the ticket were going to the candidate.
Go make a donation online. You are asked for your employer and occupation. The fact that Plame hid her employment with the CIA can either be construed as attempting to hide her partisanship or her employement with the CIA.
Still, whoever found this nugget is very good!
The concert was a fund-raiser for Kerry's campaign---buying a ticket was considered a donation to his campaign.