If there is a drop in hashing power/miner, the difficulty will decrease and therefore it would be a wise idea to buy hardware.
At this time and age wouldn't it be cost effective for manipulation by a bitcoin hardware seller? What I mean is a organized DDOS in order to make it look like there is less miners, thus people will think it will be easier to mine and will buy hardware?
Then when they shipout the hardware they stop the DDOS.
I hope this is not the case.
That won't work in practice as most miners have failover pools set in their configs.
Even if all pools are DDoS'ed, there's still p2pool, which is quite difficult to shut down.
But there can be other kind of manipulation.
Say some mining hardware manufacturer has a lot of mining power already deployed and wants to manipulate network hasrate.
It can manipulate network hasrate to a some extent by diverting some of its hashrate to PPS pools while performing block withholding attack.
So they are getting paid while the number of actually found blocks drops.
There are at least 2 pools offering PPS - BTCGuild and gigavps' private pool.
While the fees are significant, it's a lot cheaper than just turning off yor mining operations.