I see lots of talking and much less walking about online/offline integration.
Therefore when I stumble upon initiatives such as Likify, it's like a breath of fresh air.
I am sure you have been using QR Codes for a while now in your offline communication. Likify links the code to a page where attendees will be able to Like your event.
Gosh you gotta love Likes. The more Likes the more people will learn about your beautiful event.
Therefore whack a Likify code right know on your brochure and you could finally have a way to measure the ROI on all the money spent on print.