Got an email on the 27th stating that "Show of Hands" was downloaded from Taiwan. Checked the mail headers, defiantly from Apple's servers. Loaded up iTunes and sure enough that app had been downloaded on my account on the 27th.
I use pretty strong passwords (especially don't reuse PW for important accounts), keep my machines relatively locked down and regularly check to make sure my accounts -- especially email -- haven't been compromised. I haven't even had an iDevice for over a year and rarely use my Apple ID with the last login before this being around September.
A search on Twitter reveals that in the past week a number of people are reporting the same exact issue with different apps being downloaded from their account in Taiwan.
Thomas, the how is extremely important. Yes everyone should immediately follow those steps, but they are not going to matter much if Apple's system has been compromised. You mentioned brute-forcing, Apple's system locks the account after a very small number of attempts. With the number of similar compromised accounts and no reports of being locked out in just a week time frame -- I highly doubt it was a BF attack. If it was, then the attacker should be investing in some lottery tickets as he must be a pretty **** lucky person.
Ultimately, I changed my password, removed all payment information from my account and cleared out all my iCloud data. Though that's pretty easy for me to do as I no longer use Apple products.