Also, it also depends how far apart your subject and background are.
More distance between them, the more natural blur as well.
Seen at 40mm and f/2.8
Leafy Lichen by
Witty nickname, on Flickr
Seen at 50mm and f/2.5
Locked Mailboxes by
Witty nickname, on Flickr
Seen at 50mm and f/1.8
Flower Focused by
Witty nickname, on Flickr
Seen at 130mm and f/5.6
Hope by
Witty nickname, on Flickr