Ext3 and write caching by drives are the data killers...

Note that you won't get a whole blockfull of garbage: ext3 will generally
notice that 'hey, this doesn't look like a journal' once the record that
spanned the block boundary is complete. But that's a bit late...

(this is all supposition from postmortems of shagged systems. Thankfully
we no longer use hardware prone to this!)