"I also usually prefer to keep them on my local computer and not to share them with the world". You could keep it online,

"I also usually prefer to keep them on my local computer and not to share them with the world". You could keep it online, without sharing it with the world. This should be done with a transparent encryption scheme. The server stores only the encrypted version of your list. Your browser decrypts it and shows it to you, wherever you are. This should work for anything where searching/indexing is not needed. Sadly, this would remove the possibility of targeted advertising, which is the main (only?) source of profit these days.