Can you use Google Glass in the airport security line?
The TSA does not have a specific policy on this, but it does have a general stance on taking photos and video of airport security checkpoints:
Taking photographs may also prompt airport police or a TSA official to ask what your purpose is.
Not only does this policy not ban the taking of photos and video with digital eyewear such as Glass, but it actually suggest that, if you're going to do so, such wearable cameras would be the preferred method. After all, the entire purpose of Glass is to get technology out of the user's way, thus making its use faster and less obtrusive.
I've tested this theory on a handful of flight since getting my own Glass, and have never encountered a problem. I usually take the Glass off to put them through the baggage scanner, but I once wore them all the way through the millimeter wave body scanner. I almost made it through unquestioned until the agent at the other end of the scanner noticed that they were not normal glasses and told me I needed to send my "techy thing" back through the machine.
According to conversations in the Glass Explorer forums, other Explorers have had similar experiences. I have yet to read of anyone who was not allowed to take photos or videos with their Glass, although a few were questioned. And the consensus seems to be, although you might make it through the checkpoint with your Glass on, it's probably a good idea to send it through the scanner--if only to avoid delays for those traveling behind you.