reading that bug report made me cry. The use of MNG in one session of web browsing would have saved more bandwidth than used by the extra space in the installer. wtf.
Those fancy single page sites with lots of parallax effects and transformations often have 4-5 MB worth of PNGs. With JNG you can easily push it below 1 MB. (I tried this with several websites.)
To make matters worse, if you just support JNG and not all of MNG, you'd add maybe 5-10kB. The PNG and JPEG decoders do all of the heavy lifting. You'd just need a little bit of extra code for taking the file apart and splicing the channels together. All of the tricky stuff is already there.
