When was the last time you discovered a really great FOSS web application? One you wouldn't trade for a free (maybe ad-sponsored) solution, except for reasons like confidentiality or security.

For me it's Dimdim, which I discovered today. Besides Zimbra (Yahoo offers only a feature limited version of it's premium product), I can't remember any other solution in the past two years. Unfortunately.

In my opinion, the reason for the lack of outstanding solutions however is simple: If you write a groundbreaking, scalable and easy to use web application, it's a really small step to run your application on a "Software as a Service" level and earn money through ads or fees, or just sell your company. Thanks to cloud computing and a vivid community, you don't need much money to start of your business. Even a "me-too" portal is able to make it's share, if it's as easy to use as the main player. Facebook clone StudiVZ was recently sold for more than US$70 million.
Getting venture capital for a web based startup seems much simpler than finding someone who is investing in classic software distribution.

I'd really like to know which FOSS web based application you find worthy enough to disagree with me on this opinion.