Most of them will react on this, and the crack sites often do not upload again or check links, so it's a good thing if someone googeling for the crack gets dead links when trying to download.
Its some effort though. I know this problem very well. When I publish full working plugins just with a nagscreen at startup asking for a donation, even these are "cracked" by lame idiots, who think this is a great achievement.
My worst experience was to see sites selling "OEM" versions of my free plugins like Simprev....
The best way is to offer only function limited demos for free download and send the download link for the full version after purchase. Someone might use stolen credit card data or so to buy and spread, but the chance is lower and so the time is longer until you'll see a copy on the crack sites.




