I just wanted to add, as my previous responses obviously didn't indicate, I don't actually think the idea is, in essence, a bad one.   If eBay implemented a 'mark as received' button, I am almost certain I would use it, and I personally wouldn't find it any great imposition, but I feel making it mandatory or even just sending email reminders would make it an imposition for some buyers and anything that could potentially have that affect I would rather do without. If I could, I would stop eBay from sending feedback reminders to my buyers.

So that's a vote for YES but not compulsory ?? :^O