I find it very irritating to be constantly spammed by guild invites that just pop up in front of my face without ever receiving a tell asking if I want to join. It is especially irritating to be in the middle of a tough fight only to have my vision blocked by a pop-up guild invite.
Being relatively new here, I do not know how others feel about this, but I know for sure I would never join a guild that just popped an invite in front of my face without speaking to me first.
At times, I have had as many as four spammed guild invites in just one minute, two of them from the same guild, after declining the first try! C'mon people, surely you do not believe that is really going to make you any friends! All it does for me is leave me with negative feelings toward the guild.
On the other hand, only once since I have been back to AoC did I receive a very nice tell asking me if I was looking for a guild. I said I was not at the moment, but would add the player to my friends list and that their guild would be the first I would consider when I decided to join a guild. I thanked her for being so courteous, and left the conversation with very positive feelings about the guild.