Log on to just about any press-release wire service and for every release that gets it right — that is, uses two commas — there are probably eight that get it wrong, using only one comma. Even Microsoft Word's grammar checker doesn't get it. But if you were to read aloud with a nice long pause for the comma, "Snoozer Films, Inc. filed for bankruptcy," you'd take a long breath after "Films" and read "Inc." with a fresh lungful of air, as if it were a new sentence. And that would be just silly.
So if you use a comma before "Inc." you need one after it, too.
Ditto for the years in dates. "March 17, 2007, is the date that June will be celebrating her 29th birthday again."
When people leave out that second comma, which many do, I call it the "jilted comma" — a poor little punctuation mark without its mate (which has just inspired Gummy Head Joe's next single, "Hey there, Lonely Curl").