Kaled I think that you are completely wrong and it's been my experience that browser based applications are going to out number fat clients very soon.
The advantages of thin client development are many:
I can go on! All the applications that I have worked on in the last number of years have been web based. Clients that I talk to say that they are now no longer even considering fat client applications and want everything web based.
Your point about security is moot. If you are a large organisation with a web based application people will access it via a VPN (or something comparable).
You should not simply dismiss out of hand the advantages and growing popularity of browser based applications.