Okay, I'm wrong. $4 worth of stolen blankets is an offense each airline should prosecute to the fullest extent of the law. My apologies.

Your sarcasm aside, theft is a criminal offense, an offense not just against the victim but an offense against the public. In most cases, of course, the victim pursues the matter with the appropriate police and prosecuting agency, but theft is punishable even if the victim does not cooperate in the prosecution. If property is of minor value, in many jurisdictions it is labelled "petty theft," with a punishment less serious than for grand theft.

Awesome. So it's a crime. File it along with the FAs walking untold quantities of mini bottles off the plane (an offense against the public) and charging MCE passengers of alcohol (a violation of contract, false advertising / bait and switch). I look forward to the OP snapping pictures of the FAs who commit these crimes and posting them on this forum.

I remember getting a look from a FA about 10 years ago when my family and I were going on a red eye from LAX to PHL (long flight) We all had a row 2x2 in the front of coach and my wife and I dug out our US Airways flrst class blankets (the old international first when US had three class) and you could see the logo on the corner of one of the blankets. The FA was clearly wondering how we got them. FWIW, when US got rid of three class, they had a fire sale on three class stuff on the US Airways company store. Heavy duty blankets that we bought for about $10.00 each.

You have claimed above that (a) it is not a crime unless someone presses charges (b) it is not a crime if no one tries to stop it (c) it is not a crime if other people (FAs) are doing similar things also . These claims are not true. You are correct that (d) it is not a big deal because the value of the stolen items is small, but that is a different criterion you have just raised, and (a)-(c) continue to be incorrect criteria.

But is moving a blanket from one cabin to another really theft from the airline?
Am I a shoplifter if I try an item of clothing on, and leave it in the fitting room instead of returning it to the rack? I think not. Even if I leave it in a heap on the floor of the fitting room. Yes, I'm inconveniencing the staff and effectively reducing shelf stock availability for subsequent customers. But theft?
This seems more analogous to the OP's report than any common definition of theft.

You have no idea what happened there - perhaps that pax obtained a permission to take the blanket. Seems like FA saw that and took no action so i dont interpret the situation as a theft at all.

If you have a concern - voice it to fa. Do not take pictures without permission and accuse ppl of theft on an anonymous message board.

I get it. I am all over the place. My mind works that way sometimes. My initial post was based on the fact that if AA (and it's on site reps) don't care and there's no obvious policy posted (as far as I can tell, but that will sure to be debunked) then was a crime really committed? I'm not defending the guy who poached the rags. Headphones are,or used to be ,distributed free to keep. Another post mentioned life vest. That is obviously part of the hard product. Where is the line between hard product and soft product? I'm obviously not referring to the lie flat F/J product, but the cheap blankets typically in the overheads of domestic cabins.

I mentioned to QR FA that my cats would love the plush blankies in F and he handed me one...all wrapped in plastic. I wasn't asking for one...just making conversation. 🤷.♀️