Here's my best try:
.inner_shadow {_x000D_
color:transparent;_x000D_
background-color:white;_x000D_
text-shadow: 0 0 20px rgba(198,28,39,0.8), 0 0 0 black;_x000D_
font-family:'ProclamateHeavy'; // Or whatever floats your boat_x000D_
font-size:150px;_x000D_
} _x000D_
<span class="inner_shadow">Inner Shadow</span>_x000D_
The problem is how to clip the shadow that bleeds around the edges!!! I tried in webkit using background-clip:text, but webkit renders the shadow above the background so it doesn't work.
Making a Text Mask with CSS?
Without a top mask layer it is impossible to do a true inner shadow on text.
Perhaps someone should recommend that the W3C add background-clip: reverse-text, that would cut a mask through the background instead of cutting the background to fit inside the text.
Either that or render the text-shadow as part of the background and clip it with background-clip: text.
I tried absolutely positioning an identical text element above it, but the problem is background-clip: text crops the background to fit inside the text, but we need the reverse of that.
I tried using text-stroke: 20px white; on both this element and the one above it, but the text stroke goes in as well as out.
Alternate Methods
Since there is currently no way to make an inverted-text mask in CSS, you could turn to SVG or Canvas and make a text replacement image with the three layers to get your effect.
Since SVG is a subset of XML, SVG text would still be select-able and searchable, and the effect can be produced with less code than Canvas.
It would be harder to achieve this with Canvas because it doesn't have a dom with layers like SVG does.
You could produce the SVG either server-side, or as a javascript text-replacement method in the browser.
Further Reading:
SVG versus Canvas:
http://dev.opera.com/articles/view/svg-or-canvas-choosing-between-the-two/
Clipping and Masking with SVG Text: