Not everyone has the time to read everything in the forum, and if you haven't heard of anyone why would you do a search on everyone that you buy posters from. I am sure there are probably many things that I should maybe have read in this forum, but simply do not have the time to read everything. I have been collecting for about twenty years and to my knowledge it is only the second time I have been caught out - and the first time was early days of me collecting when I didn't really know any better. I look out for certain things in listings which are indicators but if someone openly advertises their posters as originals you don't expect them to be fake - maybe that is a mistake but you cannot go through life mistrusting everyone - not for particularly cheap posters anyway.
ONe doesn't always research a certain subject until you've been caught !