I don't think I'd ever partake in one due to the risks, (people not following through, it being someone coercing me to die to bring them pleasure, etc.) but TBH it does sound nice.
The idea of having someone die with you who feels the same way on the views of the world, humanity, etc. sounds very comforting. I've always wanted someone to relate to, and if that person wanted to die with me too, I'd happily go along with them. I don't think I'd ever want to do an online pact though, probably strictly offline since it seems safer for both parties.