In what appears to be more of a marketing than a product move, Starbucks will formally allow customers to customize their Frappuccinos beginning in May, the company told The Wall Street Journal.

They'll be able to request soy milk rather than dairy, decaffeinated coffee, light syrup, more syrup, no whipped cream, more espresso -- all things that are available now, except the soy milk Frappuccino base and a decaffeinated option.

Chief Marketing Officer Annie Young-Scrivner told the Journal that Starbucks hopes customization will attract a younger crowd. It's been working on this roll-out for years, and to prepare, it's training baristas and bringing in quieter blenders.

Update 3/18/2010: There's a helpful conversation about this at StarbucksGossip.com. There and elsewhere, it's becoming clear that the new Frappuccino base mix coming in May will not include dairy or coffee, which means Starbucks will start using the fresh coffee and milk in Frappuccinos that it uses in other drinks. That's why decaf and soy will now be options. And the new base mix is free of high-fructose corn syrup.