"When we ask people about our ads, one of the top things they tell us is that they want to see ads that are more relevant to their interests," wrote Facebook on its newsroom blog back in June last year. It's also worth noting that this functionality is standard on many other major websites.
Facebook users do have the option to opt-out of the policy by contacting the Digital Advertising Alliance in the US, or the UK or Canada equivalent. This means that Facebook won't target you with personalized ads. The changes will be in affect on Android phones and tablets too. However, Facebook will still gather the data.
Recently, Android users have had their data threatened by a new wave of adware which was hidden within popular apps in the Play Store and infiltrated millions of devices. It has been a rocky week for privacy on Android.