brushing
This is a scamming technique employed by product sellers who want to boost their sales figures, thus going up in the Amazon ranking. Essentially they create false orders for their product. They can do this either by paying people a small amount to place fake orders, or by stealing the details of another Amazon customer and placing fake orders in their name. This entitles them to do fake reviews as well. But to complete the Amazon process a package has to be sent. These packages are either empty or have been found to contain seeds.
The real danger to the person receiving the gift is that their data has somehow ended up in the hands of the scammer. There have been reports in Australia recently of people receiving packets of grass seeds, toothbrushes, torches, hair clips, etc. The seeds are an additional problem because they may have come from overseas and breached biosecurity.
The people employed to do these fake sales and reviews are called brushers because they brush up the site.