user131735: Not all the nodes in the bitcoin network are connected. So that means the computational power required to attack a smaller network would be comparatively easier.
So, say we start a 51% attack on a large number of such networks. Then, in theory a single group of attackers would only need to influence networks comprising of 51% of the hashing power.
Due to cascading effect of the networks the group of attackers can take over the blockchain with considerably less computing power.
I know I am missing something....?

user131636: For practical purposes, all the mining nodes should be connected. Anyone who is running a mining node has an interest in staying connected: Otherwise they don't have access to the most recent chain and are wasting cycles on a chain that will be ignored.

131735: <p>Not all the nodes in the bitcoin network are connected. So that means the computational power required to attack a smaller network would be comparatively easier.</p>
<p>So, say we start a 51% attack on a large number of such networks. Then, in theory a single group of attackers would only need to influence networks comprising of 51% of the hashing power.</p>
<p>Due to cascading effect of the networks the group of attackers can take over the blockchain with considerably less computing power.</p>
<p><strong>I know I am missing something....</strong>?</p>
 131636: <p>For practical purposes, all the mining nodes should be connected. Anyone who is running a mining node has an interest in staying connected: Otherwise they don't have access to the most recent chain and are wasting cycles on a chain that will be ignored.</p>
