For me it depends where you live.
When I lived in London, bike security was a top priority as theft rates were really high - when parking your bike at work or even at home (there were accounts of thieves breaking in to people's homes to get keys to garages and bikes).
Strangely, in Barcelona, which has 2nd most motorcycles on the street of any European city, people are much more lax with security - at least with the normal kind of bikes and scooters that are ridden for commuting purposes.
There is an understandable, but frankly reckless and stupid IMO, practice of leaving your helmet locked to the bike, often just resting on the ground! Some people just don't care about their gear.
I leave my Rebel parked in the street near the flat where I live (with steering lock and disc lock attached), but the GSXR sleeps peacefully in a nearby garage.
hinted, the harder you make it for thieves to take yours, the better the chances are that they will move to the next bike. However, if they want it, they will have it, so make them work for it!!!