I'll put my hand up and say I have occasionally bought after a seller has sent an offer on an item I am watching.

I don't know why it would annoy anyone. All I can think of is maybe they thought that you, the seller, could see their ID because you had sent a personal message to them.

My understanding is you're sending out the messages to anonymous watchers but many buyers may not realise that and it may give them a jolt and they may remove the item from the watched list so you can't 'see' them.

The other reason is it may focus their attention back on the item and they may decide that after all, they really don't want it any more so may as well remove it from the list. I've often got stuff in my watched item list that I haven't othered deleting and it is still there monthys later till I get around to it.

Or it could be like me. I got an offer on an item and was almost going to click and buy but an ad underneath my watched list showed same item cheaper with another seller, whose feedback I looked up and found they were drop shipping from Amazon so I looked at Amazon and wowee, the item was there at $20 cheaper than anything on ebay. So that offer sent to me could well have resulted in a sale, just not to the seller who originally made the offer. As it was, I won't be buying that item at all, the amazon reviews were very detailed and turned me off.

Bottom line-keep making occasional offers, some people will buy eventually. It won't work on everyone but on some of us it will.