Many say that the web is becoming the desktop. How soon, and how completely, that will happen is anyone's guess, but it is undeniable more desktop applications are delivered through browsers. There are advantages: user interfaces don't change between operating systems, web applications aren't platform specific, and work can be done at any computer with a network connection.
There are sizable disadvantages. Who can access (or alter) information stored in a web application? Who actually owns it? Reading an application's Terms of Service is crucial on the user's end. Free Software Magazine explains why an open license is crucial for all involved.