How much data can you extract from your customers and prospects on your mailing list before you scare them away? More than you might think, especially if you market to a younger audience.

More than half the respondents to an online survey said they would give up some personal info in order to get more relevant shopping and content, and people under age 35 are more likely to blab than the over-35 set.

Here are a few data points from a new survey on online-personalization from ChoiceStream, a Cambridge, Mass. company that specializes in designing personalization systems for e-retailers and online content providers, as reported Monday in Internet Retailer's email newsletter:

-- 64% of people who filled out an online survey said they would share some of their personal preferences in order to get "a more personalized shopping experience" online

-- 56% would hand over some demographic data for the same end.

-- 71% of the 18-34 age group would provide personal preferences and 63% would share demographic data.

-- In contrast, 57% of everybody over age 35 would specify preferences, and 49% would share demographic data.

-- Although people were less likely to permit Web sites to track their clicks or purchase histories (40% said that was okay), younger people had less of a problem with (47% to 32%).

Age also determines the kind of personalized content people want online. The youngest online adults (18 to 24) wants personalized recommendations on music (45%), DVDs (29%) and books (26%).

Personalized Web search results ranked highest with over-50 respondents (35%), followed by books (30%), news (22%) and travel (21%).