An associate browsed the MaidSafe.net features page and sees the deduplication as a safety concern. I think he is working under some misconceptions/assumptions about how the system works. Here's the specific concern...
The system having the ability to identify identical data segments negates the inherent security of those data segments. In the statement, it makes it seem as if no one knows where the segments are when in fact, they are closely tracked and managed by the system. Any file you store that another person also stores will be identified as such, allowing authorities to identify users who store the same file simply by monitoring the deduplication process.
My guess would be that there is no "deduplication process" to monitor because deduplication is a simple consequence of how chunks are routed to locations in XOR space based on their hash codes, which are calculated before they even enter the network. Also, I believe there is no way for authorities to monitor a user's activity, apart from the user's computer already being compromised, since each time a user logs on they are assigned a different XOR address.
Are my statements correct, and do they fully address his concern?