Guild Perks (Guild Perks)
Guild Perks
It won't be required or forced in my opinion. Larger guilds right now already enjoy a variety of advantages in getting groups together and such. So while the new system may encourage players to take part in guilds, it can be avoided if wanted.

I have a pvp guild that is very small (about 10 members). Will it be theoretically possible to earn all the guild perks, even if we dont raid at all?
I can't say anything is final right now, but the idea (last I heard) is that there would be multiple ways to level the guild - it just may take longer for a smaller one. As expected though, we hope to do some testing on this once things are ready in the beta to get a better feel for what works and what doesn't.

Small guilds disadvantaged by guild perks?
In my experience the people who like to focus on smaller guilds don't really care what the other larger guilds are doing as they are happily doing their own thing. It also sounds like you don't fully understand the guild system and we'll have more details to help you out when we are farther along in the beta. (Source)

"Balancing" Guild Perks
I'm sure we'll be playing around with it a fair amount in the beta. We don't want it to be a mega penalty to lose the rep to where players stay in a guild they don't like - but at the same time a lot of these changes are meant to encourage guilds as a whole so we don't want it to be extremely trivial to gain the reputation to where players give no thought to guild hopping (like now). We know this may shake things up for some players but we feel it will be a better result for the game as a whole to have a stronger setup for guilds. (Source)

Impact of Guild Perks on the game
We care about all of our players. We consider many different factors before implementing new systems especially when they may affect a lot of our players. That said, we do have to design and implement what we feel is best for the game. As a random example off the top of my head, players tend to dislike nerfs, but if one class is ahead of others we will nerf that one class and not buff 9 others.

A lot of players are also afraid of change. Before they even test things out or while it's in an early stage, they will declare the world has imploded. (See talent tree changes.) None of this means we don't care about our players. We understand that things will get shaken up, this won't be the first time gets shaken up and it won't be last, but we still need to design things the way we feel they are best for the game. Players can either choose to try it out or avoid it in favor of their own style.

There may be an impact on the economy, there may be an impact on recruiting, there may be an impact on guild sizes - but the end result is likely to be very positive on the game. We aren't designing it to cripple solo players and I haven't seen anybody provide a valid example of this so far. We have made a lot of changes recently to help support both smaller and larger guilds and want players to feel special for being part of a cool guild in this multiplayer game. We are looking forward to testing this feature with the thousands and thousands of players who are (and will be) in the beta and make it the best it possibly can be for as many of our players as possible. (Source)