Why does Ether get overloaded sometimes with 12 second blocks and a gas limit that could be changed by miners? If the network starts getting clogged, theoretically can't miners increase the gas limit?
For example, with bitcoin the 1mb block size causes congestion.
There is theoretical and practical upper limits on how big blocks you can make and then tradeoffs if you start to scale upwards by just cranking up the block size
How fast mined blocks propagate across the network
Requirements for IO and CPU bandwidth to process the transactions
If blocks are made to require more processing power (not mining power) then weaker nodes might not keep up with the network. This would lead to more centralization. Furthermore if block time is shortened that would leave more orphans and minor forks.
The original Ethereum block limit was 4.7 MGas. It has been already increased to 8 MGas to avoid short term network congestion.
