As of November 2012, the blockchain is nearly 3 GB in size with a near-linear growth of about 500 MB/month (cut from exponential growth by the hard-coded block size limit, I guess).
I want to install Bitcoin on my average notebook: Downloading and verifying the latest bootstrap.dat from Bitcoincharts took some hours (5–9, I guess), but that was only 2.3 GB! Now, I’ve been waiting for Bitcoin to catch up on the last 2–3 months, in which blocks have been considerably bigger and each block takes about 5 seconds of being processed, with my CPU at ~25% and my hard drive at max workload.
This is, to be put lightly, unsustainable.
We need a system, in which an already verified blockchain can be downloaded and directly copied to the bitcoin folder, maybe in an incremental form. The source has to be trusted, for this, one needs a verifying system in which everyone can control the correctness of the blockchain and then sign it, I’d propose to use gpg keys for this.
The source can then be distributed via server-backed torrent, for example.
Is this technically possible and how?
Edit: Since I approached this with a wrong mindset, I posted kind of a follow-up question about the security risks of lightweight clients. Should an end-user download the whole blockchain? Or is a “lightweight” client sufficient?