Leaflet GeoJSON API proposal

geojson.js

var geojson = L.geoJson(data, {

	// style for all vector layers (color, opacity, etc.) (optional)
	getStyle: function (feature) {
		return feature.properties && feature.properties.style;
	},
	
	// function for creating layers for GeoJSON point features (optional)
	pointToLayer: function (feature, latlng) {
		return L.marker(latlng, {
			icon: myCustomIcon,
			title: feature.properties && feature.properties.name
		});
	},
	
	// function that gets called on every created layer (optional)
	onEachLayer: function (feature, layer) {
		var content = feature.properties && feature.properties.popupContent;
		if (content) {
			layer.bindPopup(content);
		}
	},
	
	// function that decides whether to show a feature or not (optional)
	filter: function (feature, layer) {
		return !(feature.properties && feature.properties.isHidden);
	}
	
}).addTo(map);

// add more GeoJSON data
geojson.addData(moreData);

map.fitBounds(geojson.getBounds());