I never really get the random fleet or guild invites I get in MMOs. I usually ignore those, not really offended, just puzzled why someone would invite a total stranger into their group.
At least in Final Fantasy XIV, if I get a Free Company invite, I can look up some info on the FC before I decide. But Star Trek Online has no apparent function for that, at least that I know of and could easily use. But following me around after I’ve rejected your fleet invite 3 times will definitely not win me over!