diff --git a/appnet/appnet.php b/appnet/appnet.php
index de1dd970..acbd5ce5 100644
--- a/appnet/appnet.php
+++ b/appnet/appnet.php
@@ -856,6 +856,8 @@ function appnet_createpost($a, $uid, $post, $me, $user, $ownid, $createuser, $th
 				}
 			}
 		}
+		// Don't create accounts of people who just comment something
+		$createuser = false;
 	} else
 		$postarray['thr-parent'] = $postarray['uri'];
 
@@ -1042,6 +1044,8 @@ function appnet_fetchcontact($a, $uid, $contact, $me, $create_user) {
 	if(!count($r) AND !$create_user)
 		return($me);
 
+	if ($contact["canonical_url"] == "")
+		return($me);
 
 	if (count($r) AND ($r[0]["readonly"] OR $r[0]["blocked"])) {
 		logger("appnet_fetchcontact: Contact '".$r[0]["nick"]."' is blocked or readonly.", LOGGER_DEBUG);
@@ -1049,6 +1053,13 @@ function appnet_fetchcontact($a, $uid, $contact, $me, $create_user) {
 	}
 
 	if(!count($r)) {
+
+		if ($contact["name"] == "")
+			$contact["name"] = $contact["username"];
+
+		if ($contact["username"] == "")
+			$contact["username"] = $contact["name"];
+
 		// create contact record
 		q("INSERT INTO `contact` (`uid`, `created`, `url`, `nurl`, `addr`, `alias`, `notify`, `poll`,
 					`name`, `nick`, `photo`, `network`, `rel`, `priority`,
diff --git a/fbsync/fbsync.php b/fbsync/fbsync.php
index 85859151..14de4df2 100644
--- a/fbsync/fbsync.php
+++ b/fbsync/fbsync.php
@@ -278,6 +278,9 @@ function fbsync_createpost($a, $uid, $self, $contacts, $applications, $post, $cr
 	}
 
 	if ($contact_id <= 0) {
+		// To-Do:
+		// $contacts[$post->source_id] seems to be wrong by repeated posts
+		// must be changed in future
 		$contact_id = fbsync_fetch_contact($uid, $contacts[$post->source_id], $create_user);
 
 		if ($contact_id == -1) {
diff --git a/pumpio/pumpio.php b/pumpio/pumpio.php
index 62467414..c9eb0208 100644
--- a/pumpio/pumpio.php
+++ b/pumpio/pumpio.php
@@ -888,6 +888,9 @@ function pumpio_dolike(&$a, $uid, $self, $post, $own_id) {
 
 function pumpio_get_contact($uid, $contact) {
 
+	if (($contact->url == "") OR ($contact->id == 0))
+		return(false);
+
 	$r = q("SELECT id FROM unique_contacts WHERE url='%s' LIMIT 1",
 		dbesc(normalise_link($contact->url)));
 
diff --git a/statusnet/statusnet.php b/statusnet/statusnet.php
index 7293f882..2f3f84d2 100644
--- a/statusnet/statusnet.php
+++ b/statusnet/statusnet.php
@@ -1059,6 +1059,8 @@ function statusnet_createpost($a, $uid, $post, $self, $create_user, $only_existi
 			} else
 				return(array());
 		}
+		// Don't create accounts of people who just comment something
+		$create_user = false;
 	} else
 		$postarray['parent-uri'] = $postarray['uri'];
 
diff --git a/twitter/twitter.php b/twitter/twitter.php
index b6d0d3af..d2dc4fd6 100644
--- a/twitter/twitter.php
+++ b/twitter/twitter.php
@@ -1232,6 +1232,8 @@ function twitter_createpost($a, $uid, $post, $self, $create_user, $only_existing
 			} else
 				return(array());
 		}
+		// Don't create accounts of people who just comment something
+		$create_user = false;
 	} else
 		$postarray['parent-uri'] = $postarray['uri'];