User blog comment:Bovell/Color blind assist option for Modern Warfare 3. Killstreak system reworked./@comment-3014769-20110711074624/@comment-1518024-20110714174136

Killstreak stacking ≠ Killstreaks counting towards each other.

Black Ops has killstreak stacking, which is the ability to keep a killstreak while earning another.

The latter feature is self explanatory.