At this point, brands probably feel like it would be more effective to don dinosaur costumes and shout on the street corner than to post stuff to Facebook. Brands’ organic reach has been murdered by the social network – a devastating blow almost two years ago and small cuts ever since. For those who refuse to pay-to-play, Facebook certainly feels like an echo chamber.

Most of the time you’re lucky if ten – maybe 15 – percent of your Facebook followers see your posts. Unless you pay to promote them of course, but even then results can vary.

Instagram, at least for the time being, offers brands a respite from this. If you’re a brand and you post a photo to Instagram, there’s a 100% chance that it’ll at least appear in your followers’ feeds. Whether or not they’ll engage is another story and completely up to how effective you can be – but at least your post has a fighting chance.

One hundred precent organic reach is a beautiful thing – but in the end it could turn out to be a sirens’ song.

Research firm L2 has a new report out about Instagram’s fast-paced growth among brands.

“Facebook’s News Feed algorithm restricts the organic reach of content on the platform, and is particularly punishing for brands with large followings (500k+),” says L2 in its Instagram Intelligence Report. In contrast, Instagram communities defy gravity, with no negative correlation between a brand’s follower count and engagement rate.”

L2 looked at the top 250 brands and found post frequency on Instagram is up 23 percent since the beginning of 2014.

On average, brands post 9.3 times per week on Instagram, up from 7.5 times a week a year ago. On the other hand, brands are posting to Facebook less and less. Over the same period, average posts a week feel from 11.1 to 8.8.

Plus, Instagram is growing rapidly. Brands’ follower counts grew 26 percent overall last year.

A growing user base plus unlimited reach is enough to make any marketer swoon.

Of course, there could be a storm on the horizon.

“Enamored by 100 percent organic reach, brands have dialed up efforts on Instagram – post frequency has grown 23 percent over the last five quarters. Unlike the pay-to-play ethos of Facebook, pure sweat (namely, content testing and optimization) still drives meaningful results on Instagram. For brands, these are the salad days – motivated to both preserve user experience and create scarcity value, Instagram has kept advertising on the platform to a minimum,” says L2.

And that’s true. Instagram has been purposefully cautious about crowding everyone’s feeds with sponsored posts. This gives brands’ regular, non-promoted content more visibility. When Instagram ramps up the paid ads efforts, and it’s inevitable, brands will be competing for eyes more than they’re used to doing.

And then there’s the other issue – the one that could really hurt brands’ reach on Instagram. Algorithmic interference.

Facebook owns Instagram, and you have to imagine that it’s at least a possibility that the company will adopt a similar feed strategy with Instagram as it’s done with Facebook – limit organic reach to force brands to buy ads.

L2 agrees, and warns of this very thing:

“Brands should expect that organic reach will be supplanted by pay-to-play (see: Facebook) on Instagram, and ensure the assets and skills being erected will stand when muscle (money) replaces sweat.”

Ultimately, Instagram’s 100 percent organic reach and booming user growth could be a sirens’ song for brands. A long time ago, brand pages got used to relying on Facebook traffic and engagement – as it was free and easy. Then, Facebook pulled the rug out. Now that brands are heading to Instagram and beginning to rely on the visibility and high engagement rates is provides, could the same thing happen?