Disaster to boost companies image, right or wrong?

I recently came across an interesting article about private businesses philanthropic efforts to the katrina disaster. Over $312 million, and still growing, has been donated to the relief efforts by private corporations. Aside from cash donations, many companies have contributed their expertise to water and sewer treatment, electrical shortages, medical supplies, and temporary housing needs, to name a few. Their charitable contributions are welcomed with open arms, but in many cases their motives are questioned. Similar corporate charity was displayed during 9/11 as well as the tsunami situation, but businesses are becoming more strategic in their relief efforts. They seem to be using this disaster as a way to differentiate themselves from their competitors. Openly donating millions of dollars and countless other contributions is a strategic way of building positive public opion for the company. Positive public opinion will in turn pay grand dividends in the future, possibly, and hopefully to the company, more than the relief investment. Is there anything wrong with this? Is it unethical to use a disaster to bolster company image? Well, ask the naked katrina victim who was clothed by Levi Straus, or the mother who can now clean and diaper her baby thanks to Wal-Mart, or the cancer patient who is recieving treatment from Amgen, or the disaster victim who recieved $1,000 into their savings account from Emigrant Savings Bank, or the hungry family munching on Papa Johns pizza. I could go on and on, but I think you get the point. It is critical aid, is it not? Then who cares what the motives are!