The last two MMORPGs I have tried were Darkfall and (currently) EVE Online. I was on the roller coasters for quite a few years and wanted to see what the other side of the genre was like.
I've made observations about sandbox games, particularly in the newbie areas since I haven't played either game for more than a few weeks. I will say that as complicated as EVE is, it does a much better job than Darkfall at weening the rookie off the training wheels and getting players doing at least something. Maybe it's because EVE has been around for 6 times as long as Darkfall. Or maybe not.
But there is a major fault in both these games that I want to address--namely how the player goes about becoming part of a community. Finding a joining a guild in a sandbox is very much a chore and takes initiative on the players' part (like all things in a sandbox). There are in-game and out-of-game recruitment channels, but there are no accidental recruitment channels. In theme-park MMOs, you put together a questing or experience party, you are meeting potential members for your guild. You think "hey, this guy is fun and knows how to play; I'll invite him to my guild." Done. Easy for the recruitment officers. Easy for the potential members.
In EVE and Darkfall, there is no native trial-run environment. Although there were a few spontaneous parties created around the goblin camps in Darkfall, everyone in the party was still seen as a potential enemy, not a potential comrade.
The solution is pretty simple: create co-operative environments where both guildless and guilded players can come to let their guards down long enough to get to know other players. Where players see others as potential friends and companions rather than potential backstabbers.
I know this sounds very artificial and against the open-world, anything-goes mentality of sandboxes. But with a subgenre so heavily focused on communities and relying on those communities to generate the fun ships for the players, you'd think that it would be less of a chore to get into one of these guilds.