Adding hops to the mash?

Has anyone tried this? I've dry-hopped before, and I've seen some of the funky contraptions that you can use to force your kegged beer through hops. Hell, I've even thrown whole-leaf hops into a glass of pale ale. What about adding hops in with the mash to get that over-the-top hop flavor? Would the acids in the hops negatively affect the sugars/proteins in the mash? Would they negatively affect the grain husks and give you a mouth full of tannins?

I've searched, and failed to come up with anything about this subject. Just throwing it out there.

Sure, mash hopping is done, esp. with IPA's where the IBU's get off centered. I brewed the Pliny The Elder clone and it had a mash hop in the recipe. Dude, mash hop, first wort hop (so the first running got hopped before the boil), hops throughout the boil, a crud load of aroma hops at flame out and then, are you ready for this, 7oz of dry hops 3 weeks in... 17oz of hops in all and the stuff tastes like sweet flowers (with 8.25% ABV)

It does effect mash pH. I've seen some articles on it. From what I've gathered, FWH gives identical results without having to worry about mash adjustments.