[etchalon]

TechWeek claims they were: http://techweek.com/a-note-to-our-community/

I'm taking them at their word.

"The photo in question was taken from a series of photos of event attendees that were posted on our Facebook page in March. These photos were taken at a photo booth featuring top hats, bow-ties, and other fun black-tie related props. It was used with the intent to promote and encourage attendance at the inaugural event here in Chicago."

Re-reading it, it might not have been this exact party/event, but it's clear that it's not just some stock photography of pretty women.