Yeah, I get a few of those too, actually... although one person didn't even bother to tell me, just friended me first ffff. I decided to ask who they were just in case it was a friend that forgot to tell me they got into FFXIV or something and found out they were trying to recruit all the miqo'tes for a free company. Said thanks but no thanks and moved on.
Except it is when I'm just running through the area and I suddenly get an invite. If you're going to tell me that a quick tell can clear things up, but they should be sending me the tell first, not the other way around. Even if it's just a quick "Hi!" to get my attention will suffice.
I never said it would be easier, but given that they're already going out of their way to randomly invite me, they should take the time to say "hi!". I don't like being stopped while I'm running somewhere because I got that pop up yet again. But if someone says hello, I'm more inclined to not mind as much and see what's up. So no, I don't think the etiquette would be different. Maybe things will need to be said different or in smaller amounts, sure, but whatever controller you're using, if you're the one giving out the invite, then you're the one who needs to send the Tell first. Especially if you're on a PS3 controller since you know how difficult it is to type fast. I'm more patient with typing when I'm conversing than when I'm running and suddenly, "Player X has invited you to their party" and I have to stop and potentially get caught up next to a monster or whatever else.
And, as I've said numerous times, these don't involve dungeons or instances. This is just me running around an area doing a quest or my hunting log or something. Literally, I just had someone yesterday heal me and then ask me to join their party. Thanks for the heal but no, I'm not joining your party. Sorry if I'm sounding more and more annoyed but this is getting ridiculous and people telling me that I'm being the rude one or don't have some sort of valid excuse (why do I need an excuse to not want to pause what I'm doing so I can type up, multiple times, why is Player X asking to join his/her party on a PS3 controller?). If it's important enough, they need to tell me.
But I guess I'll just be the one who looks rude for declining blind invites. :/