However, amusing it's a honest mistake being fixed, this still SHOULD NOT HAPPEN in the first place. Companies dealing with personal data need to be more careful when the ramifications of "honest mistakes" can be so serious. It's right that people are making a fuss about this and pressuring O2 to fix this.
> The funny thing is that people are often surprisingly willing to provide their phone number on more and more sites, which then makes it trivial for such services to link the anonymized identifier with the actual mobile number.
Sure, but that still doesn't excuse this.