True, but they're crap. They put out a tiny bit of light, and cr2032 batteries are expensive, hold little energy (leading to short runtimes and/or low light) and non-rechargeable.
I've carried a few extra PBSF clones with me -- they come fully ready to go even with batteries for $4-$5 -- and given them away, though that is expensive enough that I've usually just given them away to people I know.
And really, if I'm only giving somebody one light ... a headlight is probably more important than a tail light anyways, especially if their bike has some reflectors on it already. I haven't gone so far as to carry spare headlights with me with the intent of giving them away yet, though I have loaned friends my spare lights (I've always got at least two headlights on my bike when I'm riding at night.)
Actually the ones I had were upgraded from the last batch I bought. The output while weak is better than nothing which is the point. The quarter size coin batteries they use aren't going to last more than a couple months true but no matter what you give someone they likely won't replace batteries anyway. If I can find something the uses a couple AAA's, has three or more leds and can mount without the need of a tool that would be the better option.
For the time being D/X sells a set of front/back frog type lights ( using coin cells ) for about $5. While they are far from the best they are cheap and can be considered "throwaways". I buy the coin cells from the chinese so I could give a spare set of those away as well.
Hopefully if you pull someone over you won't have a language barrier to overcome. The less complicated something is the easier it is to explain ( in a minute or two ) how something like a flasher works.
If someone has a link to some cheap flashers ( < $5 ) using triple A's please point them out.