Is it possible for only one invite to be sent? For example, when recruiting someone to s guild they may only receive one invite from you, same applies to summoning, and house/guild house inviting. Would prevent spam.  

or maybe some sort of restriction or popup that says something like "you can only invite your friend once every five seconds!" unless that's already made  

For reals.... I hate when randoms keep inviting me to their guild

"pls! hey how are you! pls! pls aguzo! hello aguzo wanna join? why dont you join? i know you aren't afk, i not stopod!" *continues to watch me for more than half an hour*

I don't want to have ignore guild invs on.

The only thing I can think of is, maybe a 5 minute restriction? Or just block the person

I don't like to block people tho.  

Posted by Weeno

or maybe some sort of restriction or popup that says something like "you can only invite your friend once every five seconds!" unless that's already made

Something along the lines of not being able to send out another invite unless their current invitation is accepted or declined is more appropiate.  

I wrote my idea twice (now 3rd), about adding new option to ignore guild invites and receive friends only to reduce the spam :T