99% of the time they don't need quotes
But I'd like to encourage people to get into the habit of doing it right to prevent the occasional glitch. Perspective's URL had a few "=" characters, which the browser interprets as another name=value pair. Also, some URLs have spaces in them, and again the browser seizes upon those as signifying the end of one name=value pair and the start of another.
Plus, It's the Law. Although browsers are forgiving about the absence of quotes, in truth they're required by the international technical standards to which I, as a card-carrying Web designer, am sworn to uphold.
--Robert