Pac fights Mosely because....

[jaskieee]

... Floyd already beat him.

The way i see it Pac is way easier to hit than Mayweather and if Mosley catches Pacquiao the same way he caught Floyd in the 2nd round of their fight it will be on. I wouldnt be surprised if Pacquiao hits the canvas in their contest (but im not predicting it) but even if Shane did manage to drop Pac, Pac still would get up and force Brother Naazim to throw the towell in by round 10.

[frankenfrank]

Mosley can still pull the trigger ..
Just not in time ..

[EL_cano]

Because pacquiao is the only person that can retire Mosley.

[IMDAZED]

Because his ho's will buy it.

[Frogs!]

because he can do whatever he wants and there's nothing we can do about it.

[Weebler I]

because Mosley is a high profile American boxing star and will automatically bring in more US dollars for Bob Arum than the alternatives.

[The Gambler1981]

Mosley can still pull the trigger ..
Just not in time ..

Mosley can pull the trigger just fine until he gets flustered.

The main problem for Mosley is he is semi-auto when being fully automatic would help him greatly.

[Allucard]

To add another big name to his record. Pac wants to have a W over all the big names of this era.

He failed to have a win vs Agapito Sanchez though.

[IronDanHamza]

Because his ho's will buy it.

I Include this to my post.

[Vegan101]

the only logical explanation is...

because Gayweather is too shook to fight Pac.