It's been happening to me quite a bit lately. I just upgraded my internet service and I thought maybe that was an issue. but seeing how many others are getting the same issue, I'm thinking it's on the other end.
If I switch lobbies between matches, I'll be in the lobby all by myself with the systems saying "waiting for host". And I wait, and wait....and then I get disconnected from the servers! Sometimes it even disconnects me from the PSN. Been disconnected in the middle of matches quite a bit lately, as well.