One of the principles of a bicycle helmet is that if you crash on your bike and land on your head, the helmet absorbs the force of the crash, breaks and saves your skull from fracture. You can walk away to tell the story.
There is a definite analogy here in the world of data security breaches.  Believing that you can actually prevent a hacker from exploiting your rich Web 2.0 application vulnerabilities by installing the system on a Tier 1 PCI-DSS-certified cloud provider is not a substitute for knowing in real time that an event took place.
Implementing a set of practical, up-to-date security countermeasures for your software vulnerabilities, including real-time data loss detection is far more important than multiple defense in depth layers that attempt to prevent data loss.
With practical, up-to-date security countermeasures for your software vulnerabilities you will minimize your attack surface.
With data loss detection, you will spot the intruder coming in a back door and walking out the front door in real time. This will place you way ahead of typical organizations that take anywhere from 4 weeks to 6 months to discover a data breach. Your primary response within the first 24 hours of a data breach is the most opportune time to minimize the damage by shutting down whatever vulnerability was responsible (usually a trusted insider or a common software bug).
The analogy with a bike helmet is inescapable as I discovered myself in the summer of 2008.  One Sunday in June, I went out for an easy 1 hour ride in the Ben Shemen forest not far from our home in Modiin. You don’t have to get into the car, it’s about a 15′ ride to the entrance to the forest – and you then have an infinite variety of circuit trails, singles and cross-country rides of all levels of difficulty.
I chose a path I’ve ridden many times – from the entrance to the forest across from the Ligad office park into the Neot Kedumim Biblical Landscape Preserve and back. Coming back, down the first hill – I went up a small dirt ramp at the entrance to a path. The front wheel went up, I went over the ramp, flipped over in mid air and made a two point landing on my head and right shoulder.
It’s one of those situations that happens in a split second – your brain registers that it is not going to end well, but it’s too late. The next thing you know – you are flat on your side and picking dirt out of your ear, and looking for your glasses.
In my case, I got up and felt blood on my face and ear – I spent the next 15′ looking for my glasses. Just as I found them – another rider came by and asked me if I was ok – to which I smiled and said – “of course not!”. He gave me a Wet ones he had in his backpack from Turkish Airlines and I wiped down my face. We rode back to the exit from the forest together and I rode home. Oren from Kfar Oranim – you’re a Good Samaritan man – thanks!
Got home, took a hot shower, soaped down the scrapes with antiseptic soap and iced the bruises. Went over to the doc in our local medical service. After a neurological exam and x ray he gave me a clean bill of health (no breaks, no concussions) and remarked that I was the third rider he’d seen that morning and by far the ugliest crash victim of the three.