At least one title in XI already provides an in-game bonus:
When a player earns the title "Babban's Traveling Companion", Lycopodium following the person will use a Regen move on that player, which gives 3 HP/tick for 3 minutes.
There's at least one other instance where you need the right title for something to happen: To unlock the "sky" warp you need to set your title to "Warrior of the Crystal" for the portals to register you.
With the amount of titles and the difficulty of testing them all, there might be a number of other bonuses hidden within title that nobody has figured out. Edited, May 5th 2010 9:52am by Lianda
Exactly what I was going to mention.
Titles in FFXI are a blast, but I would definitely ask for what others have requested too. A personal list to choose from that grows with each addition (in lieu of an npc holding a select few that you have to pay to reequip), as well as a system where you can lock your title in place.
I loved running around with the title Bye-bye, Taisai for killing Taisaijin shortly after it's release. There was so much confusion on the mob itself and it was so ridiculously rare to even see the thing that it started a lot of good conversations. It's something like having a very unique piece of gear, people would like to know about it.
It made for some pretty funny situations, actually, including a large group of JPs all /cheering me after one saw the title, which cracked me up. :P It was just annoying when some little fetch quest would paste a new title there instead.
But.. I wouldn't mind seeing some more effects tied to the titles, like the one listed above. I would not want stat boosts or other things that might give an edge... but little things that could be considered fun, or extra... things that wouldn't interfere with the game, I wouldn't mind. And perhaps the effects list for the titles would just be added along with the title itself, so you could choose a title and effect as you earned them. I don't know... it would just be a lot more fun to collect each and every title that way, in my opinion.
As it is right now in FFXI, the only titles worth REALLY getting are the 2 mentioned and the ones that are extremely rare in the game... or perhaps just one that strikes you as funny. The rest happen incidentally. I'd like to see them as goals themselves. Little rewards like cosmetic changes (maybe even some costume stuff or recoloring), or pointless enjoyable little extras would be pretty neat. Perhaps you could wear a title that gives you a JA with a 24 hour cooldown that puts you in a bunny costume for 5 mins on use (like enchanted event gear). :P Just something small.