1. It takes space on a server to host the mods. PC users get the mods for free because the mods are hosted on a website that gets paid for advertising. Console mods would not be on a website. No website = no advertising revenue = no free mods.
2. Games on the console are designed to use the maximum resources available. PC games are not. Most mods are designed to use close to the maximum resources available on a PC which can be several times the amount available on a console. Even simple retexture mods designed for the PC would cause your console to run like tar in a blizzard (and that's assuming it doesn't simply crash your console).
3. Microsoft and Sony care about their image. You can put out mods that contain all sorts of AO rated material and they will be hosted because mod hosting websites don't have to try and pretend they are family friendly. Microsoft and Sony need to protect that image because they sell things in many different markets and therefore content management would be required. This means that they would have to either
A. Pay someone to design a system to filter mods and then review the remaining mods before allowing them to be downloaded.
B. Pay someone to review every single mod submitted to them before allowing them to be downloaded.
The important thing to note is that both options require them to pay... that cost will either be a deterrant, or will be passed on to the consumer.
4. Mods can cause your game, OS, or hardware to fail. These failures can be debugged on a PC but can permanently ruin a console (since you can't even attempt to fix them since you are locked out of the OS). Microsoft and Sony don't want the public relations nightmare that would exist if mods they allowed to be downloaded caused console failure, game lockup, or save file corruption. Therefore, they would never allow any mods that have compatability issues or in any way interfere with each other. Do you know how they would know if a mod had compatability issues or interferes? By testing every conceivable combination of mod installs that utilize a resource. You have to pay someone to do that.
In essence, mods are not possible on consoles, regardless of what Todd says he would like to do. The only way we could ever achieve mods for consoles would be if they:
A. Developed a special console version of the CS that was much more limited than the PC version in order to tightly control what aspects of the game could be changed. Development costs money and therefore the console CS would probably cost money to use.
B. Gutted future games and/or the CS so that once the game is finished there is very little that can be modded.
Long story short, if you want mods, save up for a PC.