Finally, I found an English language article on this:

[Quote:]

We could use a few of these on Hollywood Boulevard, too. Jasper Steutel writes,

This is a photo of a new street sign in Amsterdam which locals and tourists will see appear in some neigbouroods.

The accompanying article is in dutch but says so much that a neigbourhood in Amsterdam has put up these new signs and is also selling the signs to other neigbourhoods for 80 euros.

The text under it reads “blowverbod,” which your travel dictionary would translate as “blowing forbidden.”

They’re now being sold, proceeds to a charity, because the original sign got stolen a few times.