Comment 39 for bug 259830

#36 says that the Facebook widget uses webkit. I found the following regarding webkit and gnome proxy settings:
https://bugs.launchpad.net/ubuntu/+source/pywebkitgtk/+bug/424833 links to https://bugs.webkit.org/show_bug.cgi?id=25263 and the bad news is, that they won't fix because the problem seems to be in libsoup. There is also a bug filed under https://bugzilla.gnome.org/show_bug.cgi?id=605048

Maybe someone can sort this out. For me qwibber is rendered useless at this time, because I need to have a proxy.