Since today the image uploader inserts an image using:
![enter image description here][https://i.stack.imgur.com/blah]
I'm sure that the previous default value, alt text
, made no sense and almost nobody changed it to something meaningful.
So how about to change it to the same URL as image's URL? i.e.

which will make sense for a person with turned off, etc images.
http://i.imgur.com/tJWuU.png
is any more meaningful thanalt text
?tJWuU.png
? And what browser are you using that displays the alt text when images fail to load?