The main reason why Firewire never took off (at least, in regards to the wide-spread acceptance for USB), was that at the time that Firewire debuted, not only was Apple wanting to charge a per-port licensing fee, but it also cost extra to integrate Firewire into a system. Around the time that Apple was trying to push Firewire, I believe chipset manufacturers were already beginning to incorporate USB into what was then the southbridge chipset, resulting in no additional costs for motherboard manufacturers. If I recall correctly, USB was also developed by an open consortium of companies, and thus it was agreed upon that there wouldn't be any licensing costs for implementing the standard itself (strangely enough, I do think they require you license the USB logo though if you want to use it, LOL)
To implement firewire usually meant adding in another chip to provide that functionality, and if you're having to pay for that + a per-port cost to Apple for each Firewire port used, you can see how that would quickly add up.
I think Apple ultimately reduced the amount that they were asking for, but by then it was too late, as manufacturers had become embittered. The only reason Firewire survived was because Apple hardware was extensively used by so many professionals, that it made sense to incorporate Firewire as the connection standard for professional and semi-professional AV devices.
(Also, don't consider this as a knock on Apple in terms of them trying to get royalties for Firewire. Most companies try: sometimes they're successful, sometimes they're not. In this case, Apple generally wasn't successful).
And yeah, I wish Apple would implement eSATA too
