Many, including me, would say SL is not a game - it has none of the structures of a traditional game. It is easiest to define it by its very name: It's much more like a second life, with structures and activities that are basically 100% your choice.

Becoming part of the SL economy is not required, although very few people don't shop at least occasionally in my experience. Becoming involved in the economy at the sort of level of stock exchanges, banks etc. is certainly a minority activity - just like in real life - but it's obviously of interest to some.

What makes Second Life gripping? I don't think there is a single answer to that. My answers about why I'm still in SL have changed over the 3+ years I've been there. And I've been in SL basically on a daily basis over all of that period.

One of the reasons I would say has persisted is the contacts with people, the friendships and the like, so the social networking if you want a posh term. But it's more than just that - facebook and the like don't do it for me - there's something about that 3D presence as well which makes it more compelling. Although not for everyone, one of the additional things in the mix for me is that I work in SL, about 90% of my RL income comes from working in SL, but this hasn't been a consideration for all of the time.

I'm sure if you ask our other SL writers, you'll get different answers though.