Well, if by invest you mean "buy and hold bitcoins," that's really more speculation (not that speculation can't technically be investing.) I'm not that big on speculative investing, which is partly why I don't buy stocks, etc. in the hope of selling them for higher prices later. So there's no way I'd put huge amounts of money into buying bitcoins. That said, if I see something that looks solid, I'll "invest" a little... so yeah, I am sitting on some bitcoins for that reason.

As far as investing by creating a bitcoin-oriented business, that can be more difficult and require more time, effort and expense for a lot of folks (although I see no reason why most of us here can't buy a few extra bitcoins, stash a little extra cash, and advertise that we're exchanging bitcoins: buying from and selling to others locally. The market can use the extra liquidity.)