Mostly yes, though you can wing it a little bit by relying on swap and/or doing any big filtering operations up front. In my work, it's never been a problem, because you can cram a lot of data into 16 GB, millions of big polygons and metadata. Note also that textual formats like GeoJSON or WKT are incredibly wasteful of space because all coordinates are encoded as characters instead of floats or integers, whereas the in-memory representation is much smaller, so even huge source files are likely to fit in memory just fine. But judging by the sibling comments it does look like it's a limitation for some.