Just going with the principle of the least amount of surprise here. This is simply what the vast majority of websites do because it's good enough. It doesn't of

Just going with the principle of the least amount of surprise here. This is simply what the vast majority of websites do because it's good enough. It doesn't offend any one too much. I'm well aware of the full range of complexity offered in e.g. the vcard standard. But dumping that on the user might not work out the way you want either. There are also some cultural differences of course with E.g. Asian people using their family name first instead of last. But going with the number of fields: 1 is probably under-engineering it, 2 is probably enough, 3 would be a stretch. 4 or more is probably over engineering the problem (unless you specifically have a requirement for this).