Recently, we ran some audits of our ARP system and discovered a few exploits. Those exploits have been patched out and we're monitoring for any issues related to it. In the process, we also removed a lot of ARP that was erroneously awarded to some members. The majority of accounts that lost ARP were bad actors purposely exploiting the system. Others, who were innocent - which I assume is everyone reading this - were also effected from the exploits by gaining ARP from votes that were maliciously given to you. You "others" did nothing wrong and are not being punished. However, if you were the benefactor of someone using this method on your posts, you will no longer have that ARP.
This means that some will notice a couple dozen ARP lost. A few others might even lose a couple hundred. But in the end, its all about the friends we made along the way.