It was at 2am on a weeknight (BST), noone who works or studies is going to take part in something that was not likely to finish until 4am. I might stay up for an official event at that time, if it was held on a Friday/Saturday night. A player event, possibly.
I also have my doubts about whether this event is right for us - how am I to know that in the near future, any of the other guilds invited might be our enemies? This event will be a double-edged sword: we will learn a few tactics against other players in gvg combat, but at the same time so do our enemies. We might learn their weaknesses if we pay attention but they will also learn ours.
Maybe if we'd known who was taking part it would have swayed me towards going, or if it was 4 guilds, or if there was a non-aggresion pact or something.
Currently there is a friendly atmosphere between most guilds and in that climate this event is a good idea. When outposts are released, and push comes to shove, things may be very different.
Another point is that some guilds may try and use diplomacy to protect their outpost or hire other guilds to do the dirty work for them. I think a lot of Ryzom players aren't into pvp in general, so they're not going to go for this event. I hope that these non-aggressive players can still hold an outpost. Maybe they can be influential enough to have supporters even in the 'enemy' guild, or in enough other guilds who will readily defend their outpost giving any single guild of attackers absolutely no chance of success. Maybe one day we will have player leaders who we pledge allegiance to
