The World_Street_Map service has a spatial reference of 102100 (Web Mercator) and the coordinates that you supply are in geographic (4326). You can resolve the problem by specifying your extent in geographic then using esri.geometry.geographicToWebMercator to convert the coordinates. Here's a code snippet that shows this: var initExtent = new esri.geometry.Extent({"xmin":-122.46,"ymin":37.73,"xmax":-122.36,"ymax":37.77,"spatialReference":{"wkid":4326}});
map = new esri.Map("map",{
extent:esri.geometry.geographicToWebMercator(initExtent)
});