So even if you keep your own coins secure, there is still a danger of theft performed with violence. You have heard of people who were forced to give up their coins/keys under duress.
Does this mean that multisig is a must?
if you have a couple of thousands bitcoin and you publicly announce it you might get mugged. but robbers don't know what bitcoin is or who has what to target them.
how can a robber know that you have bitcoin to target you and force you to reveal your keys?!
If your computer gets infected with a virus it could reveal your identity, address, and how many Bitcoins you own. I remember vod had his computer infected and said the hacker behind it stole a few Bitcoins he had stored on it.
Imagine if he had thousands stored offline and the hacker found out about it. He might have sent heavies down to vod's house to steal them off him.