I always thought "paying it forward" spoke of acts of charity, not investment (and to those who say that VCs don't expect any reward and invest solely through good spirit, perhaps they should then be making investments that don't give them the potential of huge paydays?)

Interestingly though, a read of "paying it forward" in wikipedia - https://en.wikipedia.org/wiki/Pay_it_forward - teaches me that the phrase can also be implemented in the contract law of loans. I never knew!