Carrot Popularity Statistics
CJam, 18
qN/{_'^e=$\;}%$e`p

2 bytes eliminated thanks to Martin :)
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Explanation:
q         read the input
N/        split into lines
{…}%      transform each line as follows:
  _       make a copy
  '^e=    count '^' characters in the string
  $       copy the corresponding earlier line from the stack
           if 0, it copies the current line again
  \;      discard the current line (from before the copied line)
          * after the loop, all caret lines have been replaced
          * with the original messages they agree with
$         sort the messages
e`        RLE encode
p         pretty print