While it's not ideal that my phone's battery won't last as long there is another issue which Dan touches on and I won't repeat. But it restricts who can view your site. Quite often people forget the internet is global and not everyone lives in San Francisco.
Another reason I dislike the bloat is more often than not it adds nothing. Share bars, flashing and moving content. These distract, constrict the viewing area and generally make reading much harder. Reproducing browser functionality is just bad programming. This is reinventing the wheel and often less efficiently and to not benefit to the user. As fun as it may be to add a new feature on your website please consider if it exists already. Especially if it's a back button.
On a lighter note, he's also plotted the performance of various terminals and Emacs does quite well.