I've read of a couple versions of this:
http://www.treehugger.com/corporate-responsibility/exxon-wont-pay-cleanu...
If conventional oil is transported in the US, there's a tax to ensure that cleanup of a spill will be paid for. There's no equivalent for unconventional sources of oil-- tar sands oil, dilbit, etc. This is doubly worrisome. One-- oil is oil, and is a mess. Two-- unconventional oil is harsher on pipes than "sweet, light crude", so there will have more breakdowns.
Please remove loopholes from transport of unconventional oil, such that it is taxed and regulated in the same way. If nothing else, oil companies will maintain these pipelines properly, to ensure no future toxic, deadly spills.