Yeah I get them once a week. I typically decline them and woudn't mind so much if I first gor a PM with a "hi how are you". I'm actually looking to join a fleet and cold invites are a bit of a put off.
I think any invite that does not include a quick tell asking first is rude. I usually give the invite the same amount of attention to to politeness that the sender applied to me....I ignore it.
On the other hand, if someone sends me a tell asking if I am interested, I politely tell them my answer and may even strike up a conversation and a friendship.
+1. I always ignore the random invites. If someone send me a tell, I'll politely say" no thank you".
This is how I found the fleet I'm in: Guy sent me a tell asking if I was looking to join a fleet. I said I wasn't at this time. We chatted a bit. Over the next few days, I did some missions with him as part of a team. Through this, I discovered they had a good group of people and joined their fleet.