And they didn't even do anything! Square-Enix announced some more info on the "Synergy" thing they're adding in a second (late November) update.
Because you'll apparently need certain synthesis skill levels in certain synergy recipes, the FFXIAH.com page for your own LS member's crafts just got waaaay more handy. Being able to search for crafters on there will also probablly be more useful than ever as well.
I'm kind of tempted to hurry and finish leveling my Goldsmithing (47) and Smithing (50) to 60 in case they end up being useful as well.
Under the "Synergy Skill" section it kind of sounds like Square-Enix is making the contract synthesis that some people do and the "synth for a friend" thing sort of more official. Like how people used to organize their own in-game weddings and Square-Enix eventually got around to offerring it as an actual service with signed Rare/Ex rings and fireworks.
As for the acutal "synergy" how it works with the Synergy Furnaces in towns is explained in "Synergizing via a Communal Furnace." From the sound of it after getting a key item you'll be eligible to form a party with people with different synthesis skills, get in line to use the synergy furnace in town, get a sufficient amount of "fewell" from the NPC in exchange for gil, and then drop in your ingredients. Only the person who got in line for the furnace can add ingredients or obtain the results.
Then there's some vague process where you need to operate the furnace and make sure it does not explode. You'd think specifics would be good here. What with the fiery death and all. It's still up in the air how it works at the moment though. Elemental balances and whatnot.
Everyone else who participates besides the person who supplied the items and got the resultant products gets...ash. Yes, "cinder", is the reward. You'll be able to trade them in for things that make you better at Synergy. Kind of circular rewards/reasoning there, but it will probably be Synergy skill +1 equipment like there is for the guilds (hats/glasses, aprons, mog house furnishings, etc). I'm betting you'll only be able to trade in a few per real life day like guild points.
Fiery death and destruction and customizable augments. I get the feeling that "Synergy" will actually be pretty popular. At least initially like Pankration. Whether it stays popular will depend on whether or not you can actually get good equipment from doing it.
If you can watch noobs blowing up Synergy Furnaces in the middle of town and die it'll at least be popular as a spectator sport. Evil people everywhere approve of Synergy.