The SOPA homepage problem boils down to the browser refusing to allow a cross-domain XHR.
But the full story is, well, icky.
http://bits.wikimedia.org/en.wikipedia.org/load.php?debug=false&lang=en&modules=ext.UserBuckets%2CmarkAsHelpful%7Cext.UserBuckets.AccountCreationUserBucket%7Cext.articleFeedback.startup%7Cext.articleFeedbackv5.startup%7Cext.gadget.wmfFR2011Style%7Cjquery.autoEllipsis%2CcheckboxShiftClick%2CclickTracking%2CcollapsibleTabs%2Ccookie%2CdelayedBind%2ChighlightText%2Cjson%2CmakeCollapsible%2CmessageBox%2CmwPrototypes%2Cplaceholder%2Csuggestions%2CtabIndex%7Cmediawiki.language%2Cuser%2Cutil%7Cmediawiki.legacy.ajax%2Cmwsuggest%2Cwikibits%7Cmediawiki.page.ready&skin=vector&version=20120118T020454Z&*
