i don't think there is anything insecure about a 1024-bit DSA key.
Yours or mine? Probably not
But a key belonging to one of the most controversial pseudonyms of all time? You can bet that someone (likely some national intelligence agency) has spent some compute-time trying to bruteforce Satoshi's key. (they probably hoped to get lucky and gave up, or they succeeded but didn't come up with a good way to use it)