I think a lot of these "hacks" were inside jobs where the owners or employees just took the money and ran. How can a cold wallet get "hacked"? Really? I don't believe it for a second.
Anyway, all of these hacks combined pale in comparison to this 1 billion dollar fiat hack:
http://www.usatoday.com/story/tech/2015/02/15/hackers-steal-billion-in-banking-breach/23464913/At least a lot of these really poorly run businesses will cease to exist. Bitcoin companies that don't take security seriously and adhere to best practices will not last long in this environment.
the security costs a LOT. Imagine that a bank can spend tens of millions and they can be hacked. How can a small-medium exchange business to hire very good programmers? impossible.
even you take the security very serious, they don't have the resources to do it.
a small-medium exchange is earning around of 5-7K per month, maybe less. a very good programmer cost around 90-100 USD/hour.
a good server administrator is the same.
the initial website costs a lot too.