There’s a bit of a storm brewing in France this morning after it was revealed that one of the country’s leading ISPs quietly released a firmware update this week, throwing in an ad-blocking option and apparently switching it “on” by default.

Rude Baguette says that “Free” pushed out the update on Wednesday morning but it’s only now that the story is beginning to emerge. According to the French blog, Free is the second largest ISP in France with around 5.3 million users, the majority of whom are now reporting that they’re no longer seeing any ads when they browse the internet.

Free admitted the existence of the ad-blocker on its official blog (in French) when it announced the firmware update, but it doesn’t give any reason for doing so, nor does it say why it decided to switch it on by default.

The ad-blocker doesn’t seem to be that great, as some websites appear to be immune to the cull according to GigaOM. However, the software does appear to be quite effective on the whole, with the majority of French sites now no longer showing up ads.

We should point out that this might be a mistake – Free has yet to respond to any requests asking why it’s done this, so there is the chance that it was switched to default by accident.

However, if Free really has decided to intentionally block ads for its customers, without asking them, then this is surely going to lead to some serious repercussions.

According to ArsTechnica, French websites are understandably a bit peeved off about the move. One blog, Numérama, raged that “Free is being totally irresponsible and threatens to bring a violent blow to an entire segment of the digital economy!”, whilst saying that the ad block seems to be affecting all of the large ad networks, such as Google Adsense, AdTech and NetAvenir.

Meanwhile, Freenews wrote a lengthy blog post calling for its readers to switch off the ad-blocker, calling Free out for being “dangerous and irresponsible”:

“Free runs the risk of jeopardizing thousands of content publishers on the web. Most free sites like Freenews rely on advertising to fund themselves. Without advertising, they would no longer exist, we would no longer exist.”

Indeed, an ad-free internet, while it might sound like a blessing, would actually be a curse were it ever to come true. Media companies in several countries are already discussing the possibility of collaborating to introduce paywalls and I’m certain that that’s not something readers would like to see more of. On the contrary, given the sheer amount of free content that the web delivers us, I’m sure that 99% of people would agree that tolerating a few ads here and there in return for it quite reasonable.

What isn’t reasonable is companies like Free – if their move was intentional – taking arbitrary steps to cut off the chief source of funding of 90% of websites out there.