For most modern web browsers, there is an option to "sync" your data across multiple devices. This allows you to carry passwords, browsing data, and bookmarks across all of your different devices seamlessly. Do you use this feature? If you don't, why don't you use it?
Yep, I use this in google chrome. I had to disable it for extensions though, as there's one extension that only really works well on one of my machines.
The only thing that I use Sync for is Facebook. That way I can sync my Facebook contacts to my phone and stuff. Otherwise, I don't want all of my private data on all of my devices.