user20967: Check this out:

The pool will not make the 51% attack of course, for they are counting money on the system;
but it's still a problem right?  

user20702: It would be a statistical anomaly if this did not happen from time to time.
With pools having over 20% or so, they're bound to find 6+ consecutive blocks every now and then.
It's not a problem. They can't really abuse or corrupt the system like this, especially since they can't plan for this sort of thing to happen on purpose. Even if they'd have 30%, it's still a rare phenomenon (like less than once in a thousand tries).

20967: <p>Check this out:</p>

<p><img src="https://i.stack.imgur.com/Jw5aI.png" alt="six blocks made by single pool"></p>

<p>The pool will not make the 51% attack of course, for they are counting money on the system;
but it's still a problem right?  </p>
 20702: <p>It would be a statistical anomaly if this did <em>not</em> happen from time to time.</p>

<p>With pools having over 20% or so, they're bound to find 6+ consecutive blocks every now and then.</p>

<p>It's not a problem. They can't really abuse or corrupt the system like this, especially since they can't plan for this sort of thing to happen on purpose. Even if they'd have 30%, it's still a rare phenomenon (like less than once in a thousand tries).</p>
