I have yet to see a VGA -> DVI converter... (what your two way arrow implies). It's not cheap to do that because you need to do an A2D conversion.

But yes, the fact that DVI-A -> VGA converters exist is why I think every device that's going to have an external monitor jack should have a (micro|mini)?DVI jack with DVI-A support on it. It can be converted to VGA (DVI-A is the analog part of the DVI spec), and to HDMI (from the digital part of the DVI spec).

DVI with DVI-A is the "universal donor" of monitor connectors.