That concern is greater still when the value of a merger is based primarily on how a company thinks they can match up customer details they're buying with customer details they hold themselves.
NHS patient data leaked, police crime data leaked, TalkTalk, British Gas and Marks & Spencer customer details all leaked.
Hacker groups like Lulzsec are currently harvesting customer details from companies like Nintendo, Epic and Bethesda for fun.
Recent hacks of customer details from Yahoo, Uber and Equifax, to name just three organisations, suggest not.
About 157,000 TalkTalk customer details, including bank account numbers, were stolen in one of the largest cyber hacks in British history.
The former justice secretary, Jack Straw, has blasted a "huge racket" of insurance companies, the police and recovery firms who pass on customer details to personal injury lawyers.
A £130,000 fine in October to Pharmacy 2U Ltd, a company that was selling customer details to postal marketing companies.
Two of the bank's divisions lost computer disks containing customer details, despite warnings from HSBC's compliance department that the bank needed more robust controls.
The hack follows the revelation from British Airways that customer details from 380,000 online transactions were stolen during a raid that lasted more than two weeks.
On top of the list of customer details, there's even more confidential data relating to the company - including internal memos, emails, contracts and sales techniques, according to Ars Technica.
Victims of the first TalkTalk security breach last November are still fighting for compensation after losing thousands of pounds – and they say they are appalled that hackers have again been able to steal customer details from the telecoms giant.
