During the past few months, the crisis in journalism has reached meltdown proportions. The Seattle Post-Intelligencer will produce its last printed edition today and become an Internet-only news source, making it by far the largest American newspaper to take that leap. Other newspapers have closed and many more are threatened. But the transition to an all-digital product for The P-I will be especially closely watched in an industry that is fast losing revenue and is casting around for a new economic model.