I have a 100% no refund policy on my plugin. Still getting around 1% of attempts to get a refund through Paypal claims but none ever made it.

Why would I refund a product costing 30 USD? Does Microsoft offer a refund for Windows 8? Does Chevrolet offer a refund for cars? Certainly not, and they are costing way more that my plugin!

It is the duty of the guy buying a S/W to take the time to read the docs, check the demo/free release if any and inquire about the plugin. You can't on one end look for cheap S/W and on the other end expect them to make the coffee without checking if they are really making it upfront...

When I see people coming to me asking for refund, I ask them : why would I refund you? Because you haven't made your job properly? My plugin works as designed and I am not advertising any feature that isn't included and working. So if it isn't what you had expected, really sorry, this is a lesson learnt for you, next time, you will take more time to read the docs!

And with regards to S/W being stealth, yes it happens. My plugin was replicated on a network of warez websites that delivers bunch of WordPress themes and plugins. It took me 8 months to have the S/W finally removed. Everytime I was managing to have the website closed, the guy was reopening it 2 days after somewhere else. Then, I finally convinced the registrar to lock the domain and the guy had to remove my S/W to be able to continue his poor business.

Not offering refund has the advantage that less people will buy the S/W by mistake and thus you'll get less questions afterwards on how to do something that the plugin doesn't perform.

I am not Studiopress or anything big like that. But still, my S/W was told more than 1.000 times and I never processed a single refund request for the last 5 years. Some said they would sue me. I am still waiting for their attorney to come to me :)