On further inspection I have seen that a disproportionate amount of this traffic is generated by requests to the join page (/join) and login overlay (/base/user/ajax-sign-in/). The public landing page (/) only follows in a distant third place. The join page is less than 31 kB in size, but with 35,000 requests in one month, it alone amounted for over 1 GB of traffic. That exceeds even what the photo sharing on the site generates.
It's too little traffic to be an attack, and it doesn't look like bots either. Most of the hits register as Windows machines with either Firefox or Chrome as user agent. There is no one source, although it seems that very many requests come from France, while most members of the site are from Germany, the Netherlands and the United States. I also get almost no search engine referrals at all.
Because this all seems a little strange, I wonder whether there is some redirection bug or something that could be causing this many requests. Has anyone else ever noticed something similar on their Oxwall site?