He examined the hidden so-called meta data in the downloaded submission which was posted as a PDF document and found this nugget: "Microsoft Word - 204481916_1_ACCC Submission by Google re eBay Public _2_.DOC". Translated it means that the PDF was created from a Microsoft Word document with the filename "204481916_1_ACCC Submission by Google re eBay Public _2_.DOC".

A few hours after Bromage's discovery was posted on the AuctionBytes website yesterday, the PDF submission on the ACC site was taken down. It returned later on Thursday afternoon, this time without the incriminating meta data. The submission was made in response to a call last month by the ACCC for interested parties to comment on eBay's application to grant it immunity from prosecution under the Trade Practices Act ahead of the PayPal changes. The US-headquartered auction company argues that the public benefits of the move - including enhanced transaction security - would outweigh any detriment to the public caused by a reduction in competition in the online payments market.

PayPal - which is owned by eBay - allows online sellers to accept credit card payments and money transfers without having their own merchant credit card accounts. Currently, merchants can also accept credit cards, direct debit, money orders and cheques, but from June 17 eBay wants to allow only PayPal or cash on delivery.

The ACCC's response to eBay's request is being closely watch around the world. eBay is using Australia as the guinea pig and a green light by the Australian regulator would lead to the change being rolled out across eBay's global network of auction sites. The plan is also not popular with many eBay users because the auction company extracts a fee for use of the PayPal system, in addition to auction fees. The Google submission was one of scores which have been posted by the ACCC onto its website as downloadable files in the portable document format (PDF).

Most of the submissions are identified as having been made by named individuals and organisations. Only a few - including the one shown to be bearing traces of Google's DNA - are listed as either "[name withheld]" or "Anonymous". The ACCC is able to categorise submissions as anonymous if the submitter can argue that there are commercial-in-confidence reason not to reveal their identity.

An ACCC spokeswoman said the ACCC had received the document from the parties in a PDF form for posting on the public register in that format. She said it was not the ACCC's responsibility to check that all the identifiers had been stripped out because the parties insisted it was fine. It stands to reason that Google would want its submission to remain anonymous.

eBay pulled its ads from the Google Adwords network in June last year after Google staged a mock party in Boston during a big convention of eBay sellers. That event was staged to protest the auction company's refusal to allow traders to use Google's Checkout payments system - which competes with PayPal.

Google subsequently backed down and the ads were restored. Checkout is currently available to merchants in UK and US. Google may have requested anonymity to avoid speculation about the launch of the service in Australia. "We're working hard to internationalise Google Checkout but have no timetable to announce in Australia at this stage," said Google Australia spokesman Rob Shilkin.

The story started to unravel on Tuesday when Ina Steiner the editor the AuctionBytes website, a US-based site specialising in the online auction market, published a story about speculation surrounding the identity of the anonymous submission. After she invited her readers to post their theories, she received a number responses. But it was Australian reader David Bromage who finally nailed it.