The iPad is designed to charge most efficiently when using the power adapter plugged into a wall socket. Read this article from Apple.
http://support.apple.com/kb/HT4060
And like Philly already said - who advertises a product and emphasizes the products limitations. That would be a first. I'm not saying that some products aren't advertised with some disclaimers, but come on. I think your expectations are a bit unrealistic on that.
The best consumer is an educated consumer. I bought my iPad about six months after the release of the first version. I read about the device as much as I could and purposely waited until the anticipated release of iOS 4. I did not want to buy the iPad until I knew it had a few more features that I wanted so I waited and continued to read about it.
Now getting back to your original point, don't you have to plug your computer into a wall socket to draw the power needed to operate it? Even a laptop needs to be recharged. The iPad is no different - it is not a phone - it is not an iPod - the comparison holds no water for me.
Finally, the fix is - plug the iPad into the wall socket with the supplied power adapter.