PWC
From Exxon's official webpage states: "Independent, registered auditors PricewaterhouseCoopers LLP..." So, PWC is the auditor.
deloitte
KPMG
The firm Deloitte & Touché LLP is the independent auditor for Twitter. They handle all of the financial statements for this company.
PricewaterhouseCoopers, LLC
Deloitte & Touche LLP
Auditor's judgement
As of their 2011 annual report, it is PricewaterhouseCoopers.
An independent auditor is asked to express an opinion on the fair presentation of financial statements because a company may not be objective with respect to its own financial statements.
aaron barry berry
who is the independent accounting auditor for acer