Do advertisers love or hate Facebook and Google?

Unilever, the maker of Marmite, Dove and countless other household brands, has threatened to pull advertising from digital platforms like Facebook and Google unless they clean up their act.

The Anglo-Dutch giant's chief marketing officer, Keith Weed - in charge of the world's second largest advertising budget - had some sharp words for the tech titans at a conference this week in California.

"We cannot continue to prop up a digital supply chain - one that delivers over a quarter of our advertising to our consumers - which at times is little better than a swamp in terms of its transparency."

He went on....

"Unilever will not invest in platforms or environments that do not protect our children or which create division in society, and promote anger or hate."

Is this genuine concern for consumers and society with a bit of halo-polishing thrown in - or is this the beginning of a genuine backlash against the giants of digital advertising?

As one senior industry insider told me "watch what they do, not what they say"

After a cut in on-line advertising spend - mainly made up of agency fees - in the first half of last year, Unilever increased digital spend in the second half.

In its most recent earnings report two weeks ago, Unilever's chief financial officer said the company was once again "stepping up" the amount of money spent on digital advertising - of which Facebook and Google are the biggest recipients.

It's not to say that the big advertisers are secretly really happy with the big digital platforms - they are not. But their problems aren't limited to the purely ethical.

There are more commercial concerns. Google and Facebook have long faced criticisms over the way they measure how effective ads placed with them really are.

Sir Martin Sorrell, the chief executive of WPP, has said that an online ad viewed for three seconds with the sound turned off has not really been viewed at all.

There are growing calls for the "duopoloy" of Facebook and Google to be regulated and measured in the same way as traditional channels - like NBC in the US or ITV in the UK.

Online ro(bots) "view" online ads, boosting viewer numbers by mimicking audience behaviour in a way that doesn't happen in other traditional channels.

Proctor and Gamble's chief brand officer, Marc Pritchard, has called this digital advertising supply chain "murky at best and fraudulent at worst".

Having said all that, P&G, Unilever and the agencies WPP owns continue to push ever increasing amounts of money towards digital platforms.

Facebook and Google account for 60% of the £11bn digital advertising market and almost 90p of every £1 in new spend is going to these two players.

Such is their dominance - what choice do they have? In many ways, the attacks from the advertisers amount to a plea - "please clean up your act so we won't be embarrassed at having to use you".

Reputational risks are not lost on Facebook chief executive Mark Zuckerberg who has pledged to "fix" Facebook by dialling down the messages from brands and companies that pepper the feed from friends and family.

He wants to make Facebook a happier place where users - and consumers - make more "meaningful" connections.

Google has introduced new tools for users to report offensive or harmful content more quickly.

Ultimately, if advertisers still don't like what Facebook and Google are doing - they do have another choice.

Sell to your consumers via Amazon. The problem with this - according to Sir Martin Sorrell - is not only that Amazon ends up owning the relationship between your brand and your customer but the balance of power between brand and retailer is upset.

With traditional retailers like Tesco - you could argue that the retailer needs the big brands as much as the brands need the retailer.

That's not true for a brand when the retailer is worth $600bn dollars and can offer it's customer cheaper, more tailored products because it knows what the customer buys much better than the brand owner does.

Whether it's a duopoly or a troika, brand owners like P&G and Unilever - perhaps ironically - may feel that it's they who don't have much consumer choice.