I'm always amused by the arguments when something like this happens because both sides get in their polarized little corners, doom cry and then something else grabs our attention and we forget all about the previous arguments.
As someone who grew up in an oil town and has spent his adult life working in the energy sector, I see validity on both sides of this one.
The producers and pipeline companies should have done more. The technology is out there for them to do more to monitor the condition of their lines but it might cost a couple thousand to buy and install it, so many project managers balk at the cost of something they don't understand and they won't be around to see function. The production operations personnel don't have the budgets that the construction groups do, and they have to prioritize what they spend money on... and usually they have other issues calling for attention too.
I had a boss who used to say "corrosion engineering is based on nothing happening" and he would go on to explain that this is why it is a hard sell to many engineering and operations VPs in the energy industry: many of them don't know if they are getting any return on investment until they stop spending the money and a failure and subsequent release occur. Then it becomes a big "oops" and they go into damage/spin control.
On the other side, the impact, even off the larger spills have more short term impact than anything else. They can be cleaned fairly quickly, and the producers do write cheques to make up for lost income etc. I remember 20-25 years or so ago, Amoco (before BP bought them) had a huge produced water (i.e. salt water) spill at Utikima Lake that killed off all the fish in the lake. There was a public outcry and Amoco had a big clean up, including paying commercial fishermen and aboriginal people who fished/trapped the area and had their livelihoods affected. 5 years later, the lake was being fished and the area was back to normal.
In short, its not a good thing when these types of leaks occur, and often, with engineering and operations groups that don't live with their collective heads up their arses, they can be avoided. But they aren't as catastrophic as some people play them out to be, and the ecosystems recover a lot quicker than many of us realize.