NONE... I receive email from certain posters that I ASK to let me know when they find or create an important post. ALWAYS.
When I opt in, I like ping lists.
When I don't opt in, they are irritating.
It's the involuntary ping lists that seem to be an abuse of the system.
I end up wasting time going to articles where folks are NOT really asking me to comment on information or events.
When on a dial up away from the t-1, it takes a LONG time to load, review then skip down till I find the articles where someone is actually asking me a question or calling me to a thread I WANT to see.
I am on several ping lists.
I am on several email chains.
I don't need involuntary spam links put in my "comments to me" page... they waste my time, bandwidth and keep me from getting to the data that is relevant.