http://sn.1w6.org/file/mk-20150119T181713-2ddjses.html

@simsa0 another aspect is that blocking never worked (or worked well) in groups: even if a person could be blocked as an individual account their dents would still arrive via the groups they targeted - something soon exploited by savvy spammers. So the problem is not only there with federation, it's also local, in local groups. Countless possible counter measures have been proposed, but most of these ideas were never implemented - too much "should" in the heads of the developers. Identi\.ca was a spammers' paradise, starting with the welcome bot who immediately gave a spammer exposure to the search engines. The fediverse is just a mostly undiscovered spammers' paradise but as the population changes, it will become more attractive and they will come.