I'm going to mix up your questions in trying to answer this yet cover all points.
We upgraded the servers sometime back to make sure we had the space for photos. Storage wise, it's not an impact. From a network standpoint, photos tend to take up more bandwidth than text of course, but again, keeping up with current technology makes that less of a problem.
As far as uploading versus photobucket (edit:, "links" to "uploads") uploads, the YT upload is preferable, not for efficiency of YT resources, but so that posts don't have dead links later on. With photobucket and sites like that, people upload, post the photo in a forum, and then after awhile, delete the photo on the other site (or forget about it and lose the account), rendering a meaningful post often meaningless to people searching for answers later. When the photo is uploaded to YT, we try our best to make sure it's never deleted.
For the person on dial-up, there is a large impact. By turning off photos in their browser, they can save quite a bit of bandwidth. The problem is that many sites (not YT) have gone to using graphics to represent real content, so when they do turn off photos, some sites will be unreadable. On classic, there is an option to let the forum software do that for you. With that option on, all embedded photos are presented as links.
Related to the dial up issue, uploading the photo to YT won't lock someone up, we downsize the photo file size to a quality good enough for the web. By contrast, when people upload to photobucket and that type of site, they may unknowingly upload print quality photos from their camera. These are excessive in size and that will lock up a dial-up user when embedded in a post. A simple photo may be a major download for a dial-up user and take several minutes to load.
Hope that covers all the questions and then some.
This post was edited by YTSupport at 06:39:14 02/21/12.