"Facebook keeps showing me these slippers, and now I feel old."

At first I didn’t even notice the slippers my Facebook feed kept throwing at me. Over a casual Friday night dinner, a friend mentioned she keeps getting these self-proclaimed “cool” slippers as sponsored ads in her Facebook feed too.

What else was she getting?

Anthony Robbins ads. Tick. So was I. And a supermarket shopping ad. Tick. Tick. She also had wrinkle treatments. I was getting an appliance review website instead. I think I would have preferred the wrinkle treatments.

‘How weird’, we thought so utterly naively over some wine and corn chips. ‘We are getting mostly the same ads.’

The following Monday a colleague at work around my age started talking about the slippers popping up on her feed.

"I get them too!" I said, rather too excitedly for an off-hand comment about slippers. "So does my friend. They're everywhere."

"Do you get them?" I asked a millennial colleague. She looked at me blankly. I ended up showing her the slippers as though that might jog her memory.

"I've never seen those slippers in my life."

She wasn't a witness in a murder trial, she just wasn't over 40 yet.

Facebook has me and every other woman I know over 40 in a little box. And that box has scrawled on the top FOR OVER 40s. THEY WEAR SLIPPERS.

Then there are other things Facebook knows about me. It knows I have reached some existential - or let's just call it for what it is, Am I wasting my life stage? How did I get here? Surely I was meant to be special by now - stage. Enter international life coach American mega man, Anthony Robbins. I swear I have been invited to every talk in the world that he is speaking at. I can get you a good deal if you want to go.

Coles also keeps me informed on mince meat specials and when toothpaste is 30 per cent off.

Does Facebook really know who I am? I like to think not, but I'm also starting to think I might go and see Anthony Robbins and maybe I should try online grocery shopping.

Listen: Mamamia Out Loud discusses the issue of mildly offensive Facebook ads. (Post continues after audio.)

Facebook runs algorithms - they are like data spiders crawling through your devices - that crunch and evaluate everything you do online. These algorithms assess your "behaviours" - what you purchase, what you look at, what you say, who your friends are... everything. Then they add to those online behaviours the information they already have on you. According to the Facebook website, that spruiks why businesses should advertise with them, Facebook also has vital data about your "age, gender, relationship status, education, workplace, job titles and more".

Oh, and also "location ... hobbies, favourite entertainment and more".

That's a lot of information.

Now it looks as though Facebook has the ability to go inside your head too. The Australian reported on Monday Facebook can now allow advertisers to target a user based on their EMOTIONS. Specifically teens.

"Facebook is using sophisticated algorithms to identify and exploit Australians as young as 14, by allowing advertisers to target them at their most vulnerable, including when they feel 'worthless' and 'insecure', secret internal documents ­reveal," Darren Davidson reported.

That would be straight out of a disturbing science fiction novel if it wasn't happening in a bedroom down the hall from most over 40 women wearing slippers.

Profiting from targeting children when they are at their most vulnerable hits slippers that have a detachable sole out of the icky, morally wrong park.

But still, the slippers will not go away.

Other ads on my feed today include:

Anthony Robbins (cannot shake the big man)

Real estate developments (I have a mortgage)

Supermarket shopping (family of five, plus extra teen in house)

Masterclass ads (OK, this does look interesting Steve Martin, Shonda Rhimes teaching creative online classes and there is even Serena Williams teaching tennis online)

A therapist finding site (what am I googling?)

So according to Facebook I'm a housebound, malcontent who eats cheap meat. Plus, I'll grab any self improvement port in my ageing storm.

I asked my millennial deskmate what ads her feed is carrying.

A millennial's sponsored ads:

Qantas flights

Golden Goose sneakers (her feet are cool, not old)

Mary's burgers (she must actually have a social life according to Facebook. Excuse me while I ask Anthony Robbins what happened to my life)

Pretty floral dresses (because that's what goes with youth)

City to Surf (for a person who eats up life, or at least still thinks they can)

Teeth whitening  (there is still time to look better)

This millennial is about energy, looks and experiences.

Another friend of mine is in her early 30s. She recently was married. I asked her what ads she is seeing on Facebook.

The answer: ovulation sticks and IVF clinics. Obviously it's time for the pitter patter of little feet.

Listen to the full discussion on Mamamia Out Loud. (Post continues after audio.)

Still, for all their fancy algorithms and access to data and surveillance methods, Facebook has made a BIG mistake: I'm over 40 and don't wear slippers.

Ha ha, Facebook. Ha bloody ha.

That's all I've got - Big Data was wrong about something, and I'm holding onto it tight with two hands that are about to make spaghetti bolognese and contemplate doing an online tennis Masterclass with Serena Williams.

Maybe I could be a tennis player.

What ads do you keep seeing on your Facebook feed?