In Nov 2011 gmaxwell a forum moderator made this thread
https://bitcointalk.org/index.php?topic=123726.0I recently asked in
https://bitcointalk.org/index.php?topic=40264.msg3237666#msg3237666 for blockchain.info to lift their game re accuracy.
Their disclaimer
"The graph below shows the market share of the most popular bitcoin mining pools. It should only be used as a rough estimate and for various reasons will not be 100% accurate. A large portion of Unknown blocks does not mean an attack on the network, it simply means we have been unable to determine the origin."
does not deter people from using inaccurate data :/
For block finders kinlo made
http://blockorigin.pfoe.be/top.php which is accurate over the last 2016 blocks, please refer to it.