Multiple engine types in the various F1 teams

Force India- Mclaren Mercedes engine from next season

Toro Rosso- Ferrari

Williams - Toyota

Red Bull Racing- Renault

This is despite that fact there are teams like Ferrari (where Massa and Raikkonen are), Mclaren (Hamilton), Panasonic Toyota (Trulli and Glock), Renault (Alonso and Piquet) are also competing. Seems that besides the front runners, the rest of the field is also a competition ground for the various engine suppliers.