Totally agree with full bike covers being a good deterrent. It stops prying eyes, they can't see what bike is underneath or what locks are on and it is another obstacle to a quick theft. I always use the JDC size large £45 premium quality on my Bonnie, it doesn't feel fully protected without it. To be honest if someone has really targeted your bike for theft they will probably succeed eventually, just make it harder for them and deter opportunists in any way you can.
Minimum 2 locks now is what I hear. I still cant believe the riders that are not helping this issue though. Today on a routine visit, the hospital I attend, not only has dedicated motorcycle parking but also ground anchors to chain bikes to on each bay, yet hardly anyone uses them. I saw bikes chained, but not around the anchor and much to my annoyance many bikes without any security at all. There was a 6 month old street twin with nothing but the steering lock to protect it (that's if it was on!!), also a bike parked up with a chain and padlock wrapped around the carrier!! I mean what is wrong with these people. I know this particular area has been targeted as I have been left warning notes from the hospital on the bike before. Sorry to rant but it does make my blood boil when we all end up paying the price through higher insurance premiums..