That's not necessarily a safe assumption. While it is far more common for quintessentially "R" movies to be neutered down to a PG-13, it is also possible for a movie that is not quintessentially "R" to be artificially hardened in ways that don't grow naturally from the material. I'm blanking on recent examples from movies, but as far as TV goes, the revival of Ren & Stimpy was sunk in large part because the creators were pressured to make the jokes more scandalous, less sly, to compete with South Park. The under-the-radar nature of the more adult-oriented content in the original show was part of what made it great.

Yeah, well that's basically what they did with The Expendables. It was shot as a PG-13 movie, then artificially changed to an R rated film is ways that are pretty obvious. Same happened with Snakes on a Plane. But Ridley Scott has already said that he much prefers the R rated version, and given the budget of Prometheus, it would make sense that given the choice, the Studio would want to maximize the audience with the less restrictive rating.

This is the real reason why the R rating is a good thing. We should all want to see Scott's intended version of the film more than another version that isn't his intended version.

The point is, studio meddling is a bad thing, whether they're toning a movie down to get a more audience friendly rating, or artificially changing a movie to give it more of an edge.

Where did you hear that? Expendables was always intended to be rated R as far as I know, I highly doubt Stallone shot it as PG-13, it didn't look artificially changed to me.

I think it's fairly obvious that most of the blood was added in post-productions via CGI. It's fairly well documented that it was originally going to be PG-13.

Interesting, I never once heard that. But even if it is true, I think it was for the best, because I doubt the film would've done nearly as well at the box-office if it was rated PG-13.

Trying to get back on topic: well judging by the Prometheus trailer(s), it looks like Ridley Scott (director and producer here) will deliver big time. O.K. the "ancient culture or alien buried inside drawings code star map invitation" is an old hat (Contact, Da Vinci Code, National Treasure, even Tomb Raider 2....), as is the holographic chart/map/plan/design (Star Wars had it in a very crude embryonic 2D version, but the idea was there, and Avatar had it full blown in 3D).
BUT: I like the look and feel of the images (I assume they represent the look of the final movie). Tons of references to Alien and even Aliens, and what looks like very convincing CGI (or is it me getting used to it?). I even have the feeling that Ridley Scott wants to out-do James Cameron (both regarding Aliens and Avatar). I only hope that the movie stays "grounded" like Alien and Aliens did. Please no philosophical or "Mission to Mars"-like "explanation" to the question: "where did we come from?". Looks like we will get another "big time greedy company representative" with a different agenda than the optimistic scientists. I always loved that theme, because it states: "the real villains are amongst us, not out there".

P.S. Nice color timing/grading in the trailer (and hopefully the movie) everything is in icy grey-geen-blue except for yellow lights and the laser-beams (back from Alien, but this time in red instead of green-blue). Nice touch!

...just my random ramblings and thoughts...

Expendables 2 was well documented to be PG-13 (backlash seems to have returned to R) but this is the first I heard of the first one being that way. A lot of blood is added via CGI these days because it can be more cost/time effective than using squibs and fake blood. Centurion was the same (although they used buckets of real blood as well).

Stallone had just come off the ultra-violent Rambo and Expendables always intended to be a throwback to the 80's/early 90's action movies. The way it was filmed clearly showed me that it was never intended to be PG-13. The rating proved to be irrelevant anyway because the movie was terrible.

Sidebar: best use of CGI blood is in Star Trek VI... because there was no other practical way to do it.