Forgive me if this is a stupid question, I may have missed something, but as far as I can tell when someone sends you a guild invite there is no way to see any further information about it (such as their 'about us' statement) until you have actually joined, unless someone posts what their particular guild is about in a chat. Obviously you can ask the person who invited you... unless they log off before you get a chance to check your notifications. Likewise it's not a big deal to just join and read what it says and if you don't like it leave, unless you already have 5 guilds, at which point a new one could be more worthwhile than one of your others, but how can you know with nothing to go on but the guild name?
It just seems like there ought to be some way to view what a guild is about by clicking on the name in your notifications, or something like that, before you actually join. It would also make it easier for someone doing the inviting if the invitees didn't need to whisper them for more information and could just look at it for themselves.