Twitter Inc.

Yahoo Inc. believes a lot of its good work has been overlooked by investors and the media so it's spending more than $100 million to get the word out to consumers directly.

The money is going toward the Internet company's most expensive marketing campaign since Stanford University graduate students Jerry Yang and David Filo started Yahoo's Web site 15 years ago. Yahoo provided a peek at the 15-month blitz Tuesday in New York.

It turns out the media elite aren't so different from a lot of less affluent folks: They think Twitter is a great communications tool, but can't figure out how the online messaging service is going to make money.

The recurring doubts about Twitter's moneymaking potential cropped up again Wednesday as an exclusive media summit hosted by investment banker Allen & Co. got under way at the posh Sun Valley resort.

Yahoo Inc.'s chief executive said Wednesday that she is open to joining forces with Microsoft Corp. so both companies can better compete in Internet search, but a deal would need a specific set of terms -- including "boatloads of money."

An obnoxious computer program that barged into Twitter Inc.'s mishmash of Internet chatter served as another reminder of the challenges facing the rapidly growing service.

The nettlesome program, known as a worm, targeted Twitter's network with four different attacks starting early Saturday and ending early Monday, according to Twitter co-founder Biz Stone.

The worm was set up to promote a Twitter knockoff, StalkDaily.com. It displayed unwanted messages on infected Twitter accounts, urging people to visit the Web site.

Twitter Inc. has spawned a new way to communicate by limiting messages to 140 keystrokes. So here's a way to describe the Internet's latest craze within Twitter's space restrictions:

It's a potluck of pithy self-expression simmering with whimsy, narcissism, voyeurism, hucksterism, tedium and sometimes useful information.

One vital ingredient has been missing from the mix so far -- revenue. That raises questions about whether the nearly 3-year-old service can make the leap from intriguing fad to sustainable business.