You should know by now that the fact that Google is serving you an advertisement does not mean that it's safe to click on it. Time and time again examples of malware being pushed via Google's AdWords program have been detected by researchers.

And while Google tries to keep these ads from appearing or taking them down if they manage to pass through the automated filters, it is seems obvious that Google is sometimes (intentionally?) slow at reacting.

Case in point: the ads for unofficial London 2012 Olympics ticket resellers.

Searching for tickets to buy for her parents, a BBC reader and her sister typed "Olympic tickets" into Google's search engine and were given a slew of results. Among those, and at the very top, there was a link to a company by the name of LiveOlympicTickets.

"It was a sponsored ad at the top of the page, so we presumed it was a trusted official site, and we spent £750 on two tickets for my mum and dad to see the 1500m, which is what my dad really wanted," she told the BBC.

She begun suspecting that the site might not be legitimate when she was contacted by email by the site and asked to fax over a copy of her signature. When she demanded to annul the buy and receive back her money, the company responded that it was not possible.

Going into damage-control mode, she contacted her bank to stop the transaction, wrote to Google, which denied responsibility for the actions of the companies who advertise via Google AdWords, and contacted the media outlet, which began an investigation.

As it turns out, Google was aware of this particular malicious ad. As the Metropolitan Police police is currently doing everything in its power to shut down sites reselling Olympic tickets without authorization, it had also stumbled upon the LiveOlympicTickets ads and site and have asked Google to remove the ad in question.

That was more than a week before the BBC made its inquiry and the ad was still up. It was finally taken down after that, but unfortunately it's not the only one for illegal sites that Google serves - the investigative team found out many more for sites that sell illegal and/or counterfeit goods such as fake passports and IDs.

As Google admitted that they are keeping the money earned from companies advertising illegal services before removing their ads, and such companies are known for offering more money per click than other potential advertisers, it should come as no surprise that Google might be not adverse to keeping them up - at least until a greater furor is unleashed by injured parties.

It remains to be seen whether this will prove to be a good strategy for Google in the long run, but until a fitting alternative to the Google Search engine is found, I'm afraid we're condemned to treading carefully when ads served by the company are in play.