3: The blockchain is 2 fucking gigabytes, and climbing at an absurd rate. If I have to download a 2GB blockchain, and 15% (or more) of all the blocks are empty or nearly empty, then why have I wasted my time downloading 300MB+ of that? The only purpose of the blockchain is to be able to securely verify transactions that have occurred, and empty or nearly empty blocks add filesize without contributing to the purpose of the data. At the rate things are going it's already going to take further development just to figure out how to keep the size reasonable, and the last thing we need is a bunch of retards being paid in inflation to spam it up faster.
Nonsense. The blockheader is tiny. 99%+ of the blockchain is transactions. The number of blocks is based on time. Empty or not the block chain will grow by (300 bytes) * 6 * 24 * 365 bytes per year = 15MB annually (roughly double that if you include the only requires tx - the coinbase).
That cost is fixed. The only thing that would change that is a avg block time other than 10 minutes.
Transactions make up the vast majority of the blockchain. This is why downloading blockchain is fast initially (first 50,000 blocks downloads within minutes but then it slows down). Those blocks are mostly empty (yup even Satoshi mined empty blocks).
Finally, if it is just a bug in one of the clients rather than someone trying to take shortcuts, then implementing a screening system would make it obvious to the users of that client that something is wrong. In that case it probably wouldn't take long for it to be fixed. If nothing is done, then we have no way of knowing.
No botnet or even conventional TH/s farm would be running the standard client. Especially not a farm (conventional or not) which is ignoring tx.