It doesn't make sense for Brink to restrict movement when SMART is all about freedom.
QFT
Also, in games like CoD, marathon was such an important ability, there was really no way around skipping it. The ability to move equally as fast as that flag carrier is quite an important trait. This has been the same with Bungie for Halo with its problems of flag juggling. Bungie tried to kill it in Reach, even though people ranted non-stop about it (both ways actually, I can't believe the pro-removal side actually was just annoyed at the announcer's voice only). There has since been a new way to do flag juggling and not slow down after dropping the flag, but I'm sure that that will get patched by 343 if they keep sprint in the game.