I was reminded today that ITA came and went earlier this month, so I've kept alive my five-year-long streak of not attending.
By all accounts, ITA is now a major event on the information theory calendar: the participants page lists over 350 attendees -- maybe a bit less than half of an average ISIT. And the ITSoc boldface names are attending; insofar as the meeting-and-greeting career implications are concerned, I suppose I should be attending too. In the past, my excuse was that ITA was an invitation-only conference, both for attendance and for paper presentation, and I had never been invited. Maybe my impression was wrong, or maybe this year it changed: it seems like the plebs can register, but papers are still by invitation.
Is there a good reason why ITA is invitation-only? It's clearly not intended to be a small gathering, and never has been: the participants page for the original workshop lists over 200 researchers. Perhaps the organizers are trying to spare themselves the effort of organizing reviews, but the IT community is reasonably self-selecting, and the Allerton organizers allow unsolicited papers.
On the other hand, I can think of three good reasons why ITA should not be invitation-only. First, I'm not sure ITA should be described as a "workshop" (which suggests "conference") if the purpose for non-invitees is to hear pre-selected lectures; that strikes me as more of a "school". Second, it reinforces the stereotype of ITSoc as a "clubby" society; as an information theorist, you are either one of the inner circle who gets an invite, one of the outer circle who doesn't get an invite (but who goes anyway to hang around with the cool kids), or a nobody. Third, ITA is killing CISS: at last year's conference in Baltimore, the decline in attendance was stark compared to past years; since CISS takes submissions, this removes an opportunity for the less-well-known to publish. Consider the impact of that on cross-disciplinary work.
On the other hand, maybe ITSoc is sending a message that there's no such thing as a less-well-known information theorist?