I too do quite a bit of buying and selling. Curiously, I have also noticed an increase in parcels mysteriously going missing. Once I have posted a parcel it is no longer my responsibility. I always get a proof of postage, and post it to the buyer if they claim their parcel never arrived. It is the buyer's responsibility to chase up a lost parcel, using the info from the proof of postage.
98% of the time all goes well. I am astonished to read though, that from May, sellers can no longer leave negative feedback. Why the hell not?? I also think sellers should be able to have a gold star rating for their buyers, just as buyers have for sellers. The time dispatched star is a complete waste of time.....I dispatch very promptly; it's not my fault if the post office take ages to deliver a parcel, yet I can get left with a crappy comment!!