I get a lot of these memo spam in my wallet. Sometimes I wondered if they are vitally people sending this or even bots. They are mainly resteem services they are talking about. I find it quite distorting when I try to check through my wallet history and find lots of these memos. I don’t regard them because I know I am just one of the thousands of people that received it. If it costs more, then this services will actually just send memos to specific targets.