According to bokordo there are seven more reasons why web apps fail… in summary:

• They’re never built.

• They’re modeling an offline activity incompletely.

• They’re ahead of the curve.

• They don’t plan for change.
• They don’t charge money

• They have no barrier to entry…at all.

• They don’t think holistically.

Read more at
http://bokardo.com/archives/7-more-reasons-why-web-apps-fail/