1.) As a for-profit venture.
2.) The add some to, and support, the Bitcoin network.

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For #2 - DO IT! One of BTC's strengths is that it is decentralized and peer-to-peer. One real (but diminishing in importance every day) risk to the Bitcoin network is a 51% attack - where a single person or group has 51% or greater processing power on the Bitcoin network. Every little bit of hashing power helps offset this risk, and the more individuals that do it, the better. But it's not a profitable venture. It just adds to the nebulous concept of "a stronger Bitcoin network".