TALPA strides forward

The main problem I see with this is that it makes every untrusted file write a probable denial of service. If you can find a plain-text string that the scanner will reject, you can probably defeat fail2ban trivially by getting ssh to log that somebody tried to log in as {the reject string}, which means that the log file now contains a virus and can't be read by most programs. Or if you email a brand-new virus to root before the mailer is ready to reject it, and the system is using mail spools, all of root's mail is in a file containing a virus (once the description files get updated). If you get a virus into a backup, the backup becomes likely impossible to restore. If you post a virus to a web form that puts it into a database, the database may stop working.

The assumption that, if a region of a file is unexpectedly blocked from being read, important system tools won't misbehave in exploitable ways is highly optimistic, considering that this currently only happens when the system has major hardware issues. I wouldn't be too surprised to hear about systems with scanning set up turning out to be vulnerable to a variety of attacks which cause the system to be unable to process security updates.

In the Windows world, there are relatively few important helper processes, because services tend to be monolithic, so there's a relatively clear distinction between what should be prevented from using virus-infected files and what should be able to help clean them up. The UNIX world just isn't like that, making it unlikely that people will be able to have non-trivial policies that don't create security issues themselves.