If the only thing worried about is visiting taverns, then people can easily friend guild mates to complete that. At least people know their guild mates playing habits, hopefully
It's been a while since I've been in a guild with other players, but if I remember right most of them discourage (or even forbid) their members from friending each other. Mainly because it cuts down on the number of people who can aid you if you keep your friends list at the maximum*. Never stopped me, of course.
*Friending guildmates gives you a potential maximum of 220 people aiding you (or for you to aid). 140 on friends list (including all guild members) and ~80 in your hood.
Not friending guild mates gives you a potential maximum of 299 people aiding you (or for you to aid). 140 on friends list, 79 in guild and ~80 in your hood.