No, the question to ask isn't whether they are legal, but whether they are illegal.

They haven't been made illegal yet by any real-life entity, anywhere.

There are laws that apply to online gambling in the US now, for example, and that made gambling illegal in SL.

There isn't a law yet that makes online virtual micropayment banks and exchanges illegal on the face of it, or certain practices illegal.

Anything said about this is speculation, or mere stabs in the dark by these real-life entities cited here about what might apply -- but they haven't really studied it.

*When* there is a real-life legal probe *and* a court decision declaring the activity unlawful, *then* you can say this. Internet lawyers stump around pompously telling you what they think is legal or illegal. They represent nothing. When a real authority pronounces, then it will be clear.