This might be useful to somebody. I was exporting my contacts from the OS X address book (by dragging them onto the desktop). This creates a vCard file, which I was trying unsuccessfully to import into Evolution on Linux. It turns out that the default vCard format on the Mac is version 3.0, while Evolution only understands 2.1. Fortunately, there’s an option on the Address Book preferences to set the format you want, after which my addresses transferred easily.