This is utter bullshit. It's the same reasoning that leads people to say that video games or guns cause violence. Web apps are just tools, you can't out-code human nature, just like you can't legislate morality. It doesn't work.
For example: Twitter is a powerful platform for sharing information. This could be leveraged for dissent or education, and it is in some ways. However, most people just follow Justin Bieber and Lada Gaga. "Bieber Fever" allegedly consumes about 3% of Twitter's entire infrastructure. (Source: http://mashable.com/2010/09/07/justin-bieber-twitter/) Take that stat with salt, but it's certainly not improbable.
There are plenty of web apps that are truly kick-ass implementations of "doing good" (http://mycharitywater.org comes to mind), but they aren't going to ever be as popular as something like Farmville, because of human nature. Making your "do good" web app kick more ass won't make people want to do more good.
For example: Twitter is a powerful platform for sharing information. This could be leveraged for dissent or education, and it is in some ways. However, most people just follow Justin Bieber and Lada Gaga. "Bieber Fever" allegedly consumes about 3% of Twitter's entire infrastructure. (Source: http://mashable.com/2010/09/07/justin-bieber-twitter/) Take that stat with salt, but it's certainly not improbable.
The argument put forth in this post is older than dirt and completely false. I'll wager a bet that this argument is just slightly older than it's cliché response, "You can lead a horse to water, bu you can't make it drink."
There are plenty of web apps that are truly kick-ass implementations of "doing good" (http://mycharitywater.org comes to mind), but they aren't going to ever be as popular as something like Farmville, because of human nature. Making your "do good" web app kick more ass won't make people want to do more good.