I think the only thing this should really matter for is guild kiosks, and as mentioned, it's better that it be based on the number of goods for sale rather than the number of active players.

Consider that you can have a full 500 player guild, all active members, but maybe only 5 of them actually have permission to access the guild bank. Now, perhaps they are in charge of making sure that other guild members get items from the guild bank--but who's to say that they're actually doing that? Of course most of them out there are doing that, I'm sure. Two of the trading guilds I'm in are very good about making sure that banked items get shared among members. But it's not guaranteed, and it doesn't matter if the members are active or not, the guild leader ultimately has control over the guild bank completely.

As for guild stores, again, it doesn't matter how many inactive people you have, if you have 50 members, but 30 are inactive, there are still 20 people in the guild that may want to use the guild store to sell to other guild members. It's less efficient, perhaps, but it's there. This only becomes a problem when said guild buys up a kiosk slot and they just don't have anything to sell. But say you have 20 active people that have A LOT to sell due to their crafting/activity/etc. Maybe as much as a traditional maxed-out trade guild...why should they be pigeonholed into an inability to participate in kiosk trading because 30 of their members are inactive? Sure, it'd be better if they had the other active members, and they should start recruiting, but what does it matter to anyone else if they have plenty to sell?

Why should it matter as far as intra-guild activities go whether or not "inactive" guilds have access to guild banks and stores? How does that affect anyone not in that guild? Just curious.