While writing this, it gave me an idea:
@pallas: do you think it'd be possible for a wallet to sync ONLY blocks that contain my own transactions? So I could get at least a complete tx history for my own wallet? I think that'd be a nice feature to have

I'm thinking about a switch in the wallet options to enable this.
I like the idea, but I can see at least one problem: to know which blocks you need to download, you'd need to download them all, then keep only the information you need. It is a bit against the original mini blockchain concept of not needing to keep all the past blocks. But, we've seen that there is at least a use case for full blockchain: the block explorer :-)