The next time you fill up a form in your bank’s local branch for change of address or credit card application, do you ever speculate that one day such info you provide could be used in third-party promotions? Maybe not, but if you do, there’s a reason to worry.

Some of Hong Kong’s leading banks were found to violate customer privacy. Hang Seng Bank and Citic Bank International were among those singled out for mishandling customer information.

Needless to say, filling up a form in the bank serves specific purposes and does not automatically mean customers are willing to receive preferential loan rates or joint promotions by similarly-minded companies. If banks are only aware of that small guarantee websites promise whenever visitors decide to subscribe for e-news: we will not sell or share your e-mail addresses to third parties. They should also bear that in mind.

Having a huge list of personal information is a juicy target for certain companies. For one, these are account holders who have assets entrusted to these banks. Additional information could provide hints on personal preferences which may interest certain industries. For example, health insurance or wealth management companies may target those who have emphasized these choices as important.

Citic Bank made a blatant violation by transferring data of more than 150,000 customers to insurers for years without their consent. Valuable information such as phone numbers, partial Hong Kong identification card numbers and others were said to have been included in the deals. In return, the bank took varying percentage of premiums for each policy converted.

Such disregard for personal privacy isn’t new. It wasn’t long ago when Octopus Card was also found liable after selling data of millions of clients to partners.

But it’s not only limited to selling or sharing of customer information that banks become responsible for breach of privacy. Hang Seng Bank kept records of individual bankruptcies for up to 99 years when eight years would have been long enough.

Other banks were also being examined for possible violations.

So the next time we fill up the savings account application form and notice it’s taking too long to finish, maybe we are justrevealing too much information we shouldn’t necessarily be sharing at all.