This question has been coming up a lot recently, pertaining to housing and those who find themselves under water. That is their mortgage is significantly below the value of the home. This is very prevalent in California, Florida, Arizona and Vegas where the value of the home has dropped by as much as 75% from the peak.
The question is, is it bad karma to just walk away? The general answer to that is no. However there is a lot to consider here, your credit, connection with the home and in different states there are legal repercussions, where you can be sued and liable for any difference between the mortgage balance and the eventual sales price. Banks seem to be prefer the short sale scenario at the moment and in many cases the shortfall is disposed of that way.
However what ever you decide to you, it is imperative that you consult with an attorney in your state, who is familiar with the many changes and the law that are going on. If this is not handled properly then it will cost a great amount of money.
Karma is not really a word I personally use, I prefer vibration or cause and effect. For example if you have active in your energy or vibration, deceit, then you take that where ever you go and the logical effect is getting deceived. Likewise with stealing, being happy, being angry.
Getting back to the housing part of this, the reality is that prices have fallen and are still falling in most places. Like the banks who give up properties, or hotels who turn the property back to the lender, the do so as a business decision, it doesn't make sense for them to continue in this situation. There is no shame, it just didn't work out, they are not a failure, the business transaction failed. A very important difference.
Now where the karma, vibration what ever you want to call it becomes an issue, at least from my perspective and most definitely legally, is when some one commits fraud, income or appraisal wise. That is what is active and you can expect some repercussions as a result.
Bottom line is, speak with a qualified lawyer first before you do anything.