Should I publish a working paper in several different websites? I understand that it is a good idea to publish my working papers and preprints so that they are accessible to other researchers. But there are many different ways to do this, e.g:


ResearchGate;
arXiv;
CiteULike;
Academia.edu;
The university website;
My personal website;


etc...

Is it a good idea to put my working papers in all these websites?

An apparent advantage is that it increases the visibility of the paper (however, with Google Scholar, I am not sure it matter).

An apparent disadvantage is that, if I update the working paper, I have to remember to update it in all these places. Otherwise I risk having old versions of my working papers flying around the web.
No, there is no need to. Uploading to Arxiv is more than enough. Your Google scholar profile finds all arxiv papers and will notify those who follow your work about your new paper. You can also add a link to the arxiv PDF in your university and personal page. That way, you will only have to update the arxiv version of your paper, without having to ever update again your personal and university webpage.

For academia.edu and researchgate I would never bother to upload PDFs. If someone is interested in your work and cannot google your name to find the arxiv uploaded version, then I doubt you will get anything meaningful or useful (e.g., citation, collaboration) from such a person, no matter where you upload your papers.