How bad is a tempdb drive failure (with multiple tempdb files on different drives)?
Nope, I'm fairly confident SQL Server will fall over - I've had a few SAN attached drives disappear with SQL Server 2005. It's possible that SQL Server may not realise until it accesses TempDB on the drive that's failed.... in pre-prod, you should be able to simulate this by dropping the drive.

Unless you've carefully assessed this, I would also suggest you carefully reconsider your 16 TempDB datafile approach. The smart advice these days is to add TempDB datafiles only when you see TempDB contention (wait stats etc). If you really want to, start with 2 datafiles on the same drive.

The most recent TempDB recommendation I saw - it's Paul Randal, so essentially Mr SQL Server himself:
http://www.sqlskills.com/BLOGS/PAUL/post/A-SQL-Server-DBA-myth-a-day-(1230)-tempdb-should-always-have-one-data-file-per-processor-core.aspx