This is a basic principle of capitalism. Companies can be modeled as an organism which responds to one stimulus - Increases and decreases in profit. While this model is an oversimplification, as some corporations have learned to see that certain levels of public outcry today may affect their profits tomorrow, it is in general still correct. These companies are still reacting to something which is going to affect their profit margin. Companies eat money, and they "die" if they stop receiving it. While a lack of income is not the only thing that can "kill" them, a tapering thereof is one of the surest signs of their impending demise.
The corollary to this statement is that companies lack morality. This is not to say that a company can not act morally, or that the individuals who make up and/or control it cannot be moral individuals. But a company which does something which appears to be totally selfless is, in almost every circumstance, actually performing some action which will cause it to get more money. In the case of making a charitable contribution, you can be sure that it is intended to operate as a tax writeoff or perhaps to improve the company's image. More often than not it's simply some kind of spin control, like Chevron's nigh-forgotten "People do" ad campaign in which they tried to make themselves out to be a great protector of wildlife. In fact, they were simply following federally-mandated guidelines, and in some cases, carrying out directions from courts which resulted from various lawsuits. The very idea of an oil company using the most common modern technology being good for the global environment is so laughable that it could fill the entire comedy quota for Must-See TV for a year. And then some.
If you want to change a company's behavior, you must reward it (by providing it with income) when it does something you like, and punish it (by causing it to experience a reduction in income) when it does something bad. However, it is always more dangerous to positively reinforce bad behavior than to discourage good behavior. As such, for example, if you appreciate the feature set of the Sony Playstation 2, but despise the actions of the RIAA, it would be best not to purchase anything from Sony. Bank of America didn't sell their controlling interest in various South African companies because it was the right thing to do; They held those rights until the early 1990s. They dropped them because they were losing customers, and thus revenue.
People often forget that consumers are the driving force behind the market. We decide, by voting with our money, what is sold, what is developed, and even what is researched. If many people buy a particular type of product, then other companies will rush to develop their own version of the same thing. If biotech is hot in the news and on the lips of the populace, then venture (vulture) capitalists will invest in biotech companies in the same way that they unwittingly fed the dot com boom and subsequent bust. They don't apparently feel that they have to understand the industries in which they invest, and the majority of investors will simply follow the buzz.
Nothing travels faster than bad news, and nothing creates buzz like failure. When Cisco brings out a new piece of hardware that has revolutionary new features, only geeks notice. When Cisco lays of 7,500 employees, the world notices. Even people who don't know a packet from a poke in the eye dump their tech stocks when something like that happens. Cisco dropped thousands of employees because their revenues were decreasing. Of course, that was because they manufactured too much back stock of the wrong products, but it could happen just as easily because people stopped buying their more defective products -- and there have been plenty of those.
So next time a company does something you don't like, immediately stop purchasing their products, and convince like-minded individuals to do the same. This is the only thing that a company can notice. Writing them a letter can help them to understand why you aren't happy with them, but if you go ahead and give them money anyway, they have no reason to change, whatsoever.