Dan is correct, of course.
I always attach photos myself, rather than linking to an external host, in part because (like Flickr) these hosts may require creation of an account just to view the images, and some users are understandably wary of any links.
My main motivation though, is that externally hosted photos are always at some additional risk. The external host could close up shop, change their internal structure such that older links no longer function, or show the images with intrusive watermarks. I find it awfully frustrating to locate a thread on a topic I’m trying to learn about, only to encounter broken imageshack links, photobucket watermarks over the detail I want to see, etc. (E.g.,
https://www.rolexforums.com/showthread.php?t=89366)
There are so many great old DD threads (here and on VRF) which contain only moribund 15-year-old eBay links, and thus no way to even see what’s being discussed …