If Web analytics is going to work, BI practitioners need data. If a large part of their customers or potential customers is opting out of revealing information about their habits, desires and personal traits, then Web analytics is in jeopardy. Not because we won't have the right tools -- we definitely do. But because we won't have complete data.
The Internet isn't going to disappear as a way to reach customers. But intelligence that excludes information on the prudent or technologically knowledgeable customers who are more likely to be concerned about security -- well, that isn't intelligence at all.
If your job involves Web analytics, have a sit down with your security chief. Learn for yourself how safe your customer data really is.