Lots of people are commenting that maybe the yellow badges might be working on something secretive that Google does not want them to share with others. But this does not make sense for 2 reasons - 1) I am pretty sure there will be some software engineers in Google who are currently working on something secretive but they will not be under these draconian restrictions of not to talk to others or call the security immediately if a fellow Googler approaches them.

2) These ppl can go home and can talk to their spouses, their friends etc. and let them know what they are working on. So making sure that they don't talk to anyone in Google during their office hours is not going to help keep their projects secretive.

So there has to be some other angle to this story which does not involve secretiveness of their projects.