I was listening to a podcast recently and the speaker described an analogy between web applications and Vitamins, Painkillers and Viagra.

Everyone knows that we need vitamins. But nobody seems to buy vitamins. Its not a hot selling product. Vitamins are like a Nice to have product.

Painkillers have got medium sale. They solve a real world problem. People with pain will buy it and use it. Its a necessary product.

Viagra is a hot selling product. Viagra is not a nice to have product, nor does it have the necessity of a pain killer. But still its market if growing virally.

Web product designers are also looking to create products and solutions like Viagra, which will spread like wild fire.