There are too few laughs on television, but with any luck Daniel and Majella's B&B Road Trip will be back on air next year, and the couple will once again be driving about Ireland in a Skoda Yeti. Daniel will claim all-important map duty, while Majella will subvert the heartlands by going behind the wheel – or as one B&B owner exclaimed from behind the curtain, "She's driving!"

Hit shows commissioned by UTV Ireland had been lesser-spotted than a yeti, but the channel did well out of the Vision Independent Productions show, which coincided delightfully with its first spot of product placement.

This everyone-wins marriage of brand (Skoda) and programme idea (comic travelogue) worked like an especially surreal dream. But product placement, and its cousin advertiser funded programming, isn’t always so benign.

At the Cork Film Festival, its influence came under a Broadcasting Authority of Ireland-sponsored spotlight when The Irish Times television critic Bernice Harrison, addressing a public debate, concluded viewers are in danger of being short-changed. A show like RTÉ's The Taste of Success, for instance, was "one big giant ad for Lidl", she said, while The Restaurant, in its TV3 incarnation, was so slathered in its promotion of sponsor Aldi, it spoiled the flavour of the dish.

Product placement, though only officially permitted on Irish television for five years, is now commonplace. It’s a commercial necessity say the broadcasters that do it, which is almost all of them.

TG4 commissioning editor Proinsias Ní Ghrainne described it as "dangerous ground" but conceded that product placement was a model of generating cash for content that TG4 would have to explore. On TV3, product placement predated the regulatory seal of approval for the practice, reaching screens via the Irish version of The Apprentice, which had a fraction of the budget of the Lord Sugar variety and so turned to brands to make ends meet. RTÉ, meanwhile, cut the ribbon on a Spar in Carrigstown in Fair City in 2011 and has barely looked back since.

Fans of television credits may have noticed on-screen the double "PP" that signifies the programme contains scenes of a product placement nature – hence the thriving circulation of the Irish Daily Mail in Red Rock. In some cases, the commercial relationships are obvious and straightforward; in others the power exerted by the advertiser over the finished show can be impossible to isolate.

So does it even matter if it's no longer easy to identify when the advertisements end and a programme begins? Some might argue it's all just froth anyway and that television has never been editorially pure. As long as Bryan Dobson doesn't start pouring Avonmore down his throat in the middle of the Six-One, a few brands here and there are fairly innocuous, right?

At the BAI debate in Cork, RTÉ Television managing director Glen Killane and TV3 director of content Lynda McQuaid seemed comfortable with the principle of product placement, arguing it was its execution that was important.

McQuaid, who before she joined TV3 was the independent producer behind The Apprentice, likened it to balancing on a tightrope. Product placement, she said, should neither compromise "the editorial" nor should it make a show resemble a "gaudy Christmas tree".

The regulator’s guidelines make no mention of Christmas trees, saying product placement must be “editorially justified”, but also that the products should not be given “undue prominence”. And broadcasters try to persuade advertisers that credibility lies in subtlety – there is little to gain from product placement so overt it has viewers groaning.

And yet brands do seem to be infesting great chunks of the schedules, whether they are paying for it or not.

Take, for example, RTÉ Two's Reality Bites documentary the Verminators from earlier this year. On paper, it is perfectly reasonable for RTÉ to shine its unique torch on the nation's struggles with household pest control. Rats make for good television. But the whole tone was one of breathless excitement for the "crack teams" for whom pest control is a "passion". According to urban myth, you are never more than six feet away from a rat. In this programme, viewers were rarely more than six seconds away from a Rentokil logo.

Many commissioning briefs now make enthusiastic noises about advertiser funded programming. In doing so, they imply that programme pitches that have signed-up a brand partner at an early stage stand a better chance of making it to air than the ones that don’t. For viewers, the first question is “How can I completely trust what I see?” and the second, equally unanswerable, one is “What kind of television is not being made because some supermarket fancied its own show?”