As to who should attend, don't worry too much about it. I would like to encourage blog software and service companies to attend also so they can understand the needs of corporate bloggers (what ever that means). I am organizing the event for the same reason.
Please comment to this post if you are planning to attend. Even if you are not attending, please pass on the news of the event.
Venture Frogs will be the location, mainly because the place has parking. Also, I felt Cafe Bastille was too noisy.