Semantic quibbling aside, let's address what alani clearly meant:
Why would anyone want to force the blocksize limit expanding at pre-set dates. Now, give a sensible reply to what was intended.
It's hardly semantic, and I'm not at all sure what he meant. Many of the arguments against raising the cap only make any sense if understood as an argument against raising the block size.
Let's start simple. Can you give a rational argument against immediately raising the block size cap to 8MB?
There's no indicator that an 8Mb limit could be of use at the moment. One big argument for raising the limit was that more transactions per second could start being handled. Which in theory could become possible under a larger block size limit but if you think about it, even right now bitcoin isn't making full use of the 1Mb limit. Increasing the block size limit to a small number at first could help study the plausible effects such a change could have with minimum risk. If you look at it carefully, the Chinese pools have been Vetoing Mike hearn's proposals for months now. BIP101 came out with 8Mb blocks after pools accounting for ~ 60% of the hashrate at the time united
against the then 20Mb blocks proposal. Now, as BIP100 started becoming more popular, more miners are showing support towards it since it's considered a less radical and more modest proposal by far. Prior to showing support for BIP100, most of those pools were showing support for 8Mb blocks, but not BIP101. It now seems like instantly increasing the block size limit to 8Mb doesn't look as attractive to miners.
In short, an 8Mb block limit could:
- Have devastating effects on the fee market
Since there's more space in each block, this space is now less valuable, fees might not be zero, but they'll be lead down to the minimum and competitiveness for fast transactions will be dead.
- Bring nodes offline and make pools/miners less reliable
The change would increase bandwidth consumption as well as HD space required to run a full node. There are many nodes that run on non-optimized hosts, if they suddenly start sucking up more of the bandwidth and HD space it's safe to assume that many will go offline. Also, pools running on weak networks would be more prone to orphaned blocks because of the blocks being harder to propagate.
I've seen people arguing that in case the block limit was raised, it wouldn't be put to use immediately as well that it would handle transaction floods better. But what if it destroys the fee market on the moment it's implemented? Sending out a meaningless transaction would now be cheaper. Plus, if nodes and miners were available exclusively to those with unlimited hardware and bandwidth, centralisation is unavoidable.