I've got a bunch of these showing up in our error logs:
```
[17-Jul-2014 13:37:35 UTC] [2014-07-17 23:37:35] EXCEPTION: (HTTPFutureResponseStatusHTTP) [HTTP/400]
400 Bad Request at [<phutil>/src/future/http/BaseHTTPFuture.php:337]
[17-Jul-2014 13:37:35 UTC] #0 BaseHTTPFuture::parseRawHTTPResponse(string) called at [<phutil>/src/future/http/HTTPSFuture.php:371]
[17-Jul-2014 13:37:35 UTC] #1 HTTPSFuture::isReady() called at [<phutil>/src/future/Future.php:39]
[17-Jul-2014 13:37:35 UTC] #2 Future::resolve() called at [<phutil>/src/future/http/BaseHTTPFuture.php:277]
[17-Jul-2014 13:37:35 UTC] #3 BaseHTTPFuture::resolvex() called at [<phabricator>/src/applications/notification/client/PhabricatorNotificationClient.php:47]
[17-Jul-2014 13:37:35 UTC] #4 PhabricatorNotificationClient::postMessage(array) called at [<phabricator>/src/applications/notification/client/PhabricatorNotificationClient.php:34]
[17-Jul-2014 13:37:35 UTC] #5 PhabricatorNotificationClient::tryToPostMessage(array) called at [<phabricator>/src/applications/feed/PhabricatorFeedStoryPublisher.php:182]
[17-Jul-2014 13:37:35 UTC] #6 PhabricatorFeedStoryPublisher::sendNotification(integer) called at [<phabricator>/src/applications/feed/PhabricatorFeedStoryPublisher.php:115]
[17-Jul-2014 13:37:35 UTC] #7 PhabricatorFeedStoryPublisher::publish() called at [<phabricator>/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php:2140]
[17-Jul-2014 13:37:35 UTC] #8 PhabricatorApplicationTransactionEditor::publishFeedStory(ManiphestTask, array, array) called at [<phabricator>/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php:751]
[17-Jul-2014 13:37:35 UTC] #9 PhabricatorApplicationTransactionEditor::applyTransactions(ManiphestTask, array) called at [<phabricator>/src/applications/maniphest/controller/ManiphestTaskEditController.php:316]
[17-Jul-2014 13:37:35 UTC] #10 ManiphestTaskEditController::processRequest() called at [<phabricator>/webroot/index.php:95]
```