I do have stickers on some of my bikes
Untitled by
Stuart Black, on Flickr
But these are just for personalization. I’m not under the impression that this is any kind of theft deterrent.
I do, however, write my name and phone number on the steer tube of the fork... “This bike might be stolen. Contact Stuart Black at xxx xxx-xxx.” I do all my own mechanical work and I haven’t taken a bike to a shop for decades. If the bike ends up in a shop, it would likely be stolen.