For months now, my GNU/Emacs has decided to sometimes not syntax highlight my source or ChangeLog files and I didn't know why.
The other day, emacs' failure to syntax highlight xaml.cpp was the final straw. I decided enough was enough with having to M-x font-lock-fontify-buffer everytime I opened a handful of source files, especially ones that I often find need to edit and/or to refer to.
A little digging later and I discovered that GNU/Emacs must have added a feature that disabled font-lock (even if you've specified (setq font-lock-support-mode t) in your ~/.emacs) if the buffer was over some arbitrary size. Either that, or they lowered the arbitrary size to something ridiculously small.
The solution seems to be to add the following line to your ~/.emacs file: (setq font-lock-maximum-size 1000000)
Feel free to append a few more 0's to that number if you find that Emacs still fails to syntax highlight any of your source files.
Update: Another Emacs annoyance can be turned off by adding (setq inhibit-startup-message t) to your ~/.emacs file. I'm not sure why this isn't inhibited by default.