ICQ is the all-time winner at CNET. It has been the most downloaded application in its history, I believe, and now Trillian has gained a lot of popularity too, since it basically extends ICQ functionality to cover MSN as well as other types of messaging providers.
Messaging has always been an important part of the Internet experience and it doesn't seem to be slowing down in growth and acceptance. Google Talk is now in the race and Microsoft has been injecting significant improvement into the mandatory MSN Messenger. But I digress.
I think Firefox and the Mozilla Foundation in general would greatly benefit with the introduction of a XUL/XPCOM based Internet messaging application. And now I have to explain why.
Just as mail applications, messaging applications are tightly related to browsing and markup rendering technologies. A Mozilla Messenger (Waterant, Lightcow or whatever weird name you might wanna give it) would greatly benefit from the existing Gecko rendering engine and all the already developed components that from the Mozilla code base. Its system-independence and simple and highly functional interface would make it as portable as Gaim and as robust as Trillian. I think this is something that might get people very excited about Mozilla products in general.
A messaging application creates a lot of buzz, and it's specially appealing to younger audiences. I think this is how Trillian gained so much popularity. I remember it was a very common name to hear when I was in college, because the admins were only blocking MSN Messenger :). Google Talk is now very popular because it's also hard to block, so it's a good way to keep an open channel through a firewalled world.
This application could benefit as well from XUL's extensibility and skinability through CSS. Most users love this stuff, specially the latter. A lot of very exciting extensions could be developed in a chat application, making it probably as powerful as MSN messenger.
Furthermore, a properly developed application could be extended to work on enterprise environments, where Windows Messenger is almost the only option. Since both Firefox and Thunderbird are already looking to immerse themselves in both the mainstream and enterprise environments, this chat application might give them additional leverage. It would be a more complete package.
There's some obvious cons, which I should also mention. First of all, this application might be a bit heavy for a simple messenger. The whole runtime required to run XUL/XPCOM applications might create bloated installers and memory hog releases. Although, checking the Trillian installer, it's already more than 8Mb, which is larger than Firefox or Thunderbird. In general, I think the memory leaks should be dealt with before expecting people to run a whole array of Mozilla products at the same time.
Another good point is that it might be most appropriate to develop this application based on the Xul Runner framework. It's still a bit distant, but it would make the application's installer and footprint almost insignificant, considering people already have Firefox.
In conclusion, I believe that developing a messaging application might attract new audiences towards Mozilla, and consequently Firefox. I wonder if this idea has been proposed before. It probably has. I think it's a good idea and deserves some serious attention. I know that the Foundation has a lot on its hands, with Firefox, Thunderbird, Sunbird, Lightning and XUL Runner, so it might take some time for this project to see the light of day. But if it does, I predict a new wave of acceptance.
I posted this on my blog because SFX is currently down. I expect to publish something there as well when eveything's back to normal.