There have been a lot of concerns about security since Google implemented lockscreen widgets in Android 4.2. Some may have concerns over how much information is actually accessible from these lockscreen widgets, and with no guidelines on what is and isn't okay, some developers are taking it upon themselves to implement some of their own security measures. Plume has decided to remove the DM (Direct Message) tab from its lockscreen widget, and now you can only see how many unread messages there are. The widget is otherwise the exact same as the one available on the homescreen.
Of course the best security policy is to not put any widgets on the lockscreen -- and use a PIN, pattern or password lock on the device -- but its good to see developers taking these things into consideration.