When u look at other main series like Nascar or Indy, if it wasn't pointed out to u that two cars were in the same team, you wouldn't know. At least, not by common paint schemes.
I think that "team mates" in F1 is more important than in most other series. Both cars are painted in the same scheme, have consecutive numbers... they're basically two halves of the same organisation.
In F1, team mates and how they work together with each other is a main part of the sport. Watching Lewis pass Heiki earlier in the season was expected. Watching Massa pass Kimi today was expected.
In both cases, I would have been disappointed if the drivers didn't work together for their net benefit.