Many of our sites perform very well in the SEO arena and we think this is at least partially due to stuffing keywords in the title tags.  These are on older sites though, and we have since tried modifying the title tags to get different rankings.

When we do that we get SLAMMED - that is, punished by Google and are wiped off the face of the earth in search rankings. 

I'm thinking that Google will punish you for doing keyword stuffing in the title tag, but old sites got Grandfathered in.  That is, Google couldn't retroactively go after all the old sites that had stuffed title tags, but they could punish any new ones. 

I haven't seen anyone else mention this.  My fear is updating a site, yet keeping the old keyword-stuffed titles and getting whacked for it.  This is for a big site that currently has a prominent position in google. 

Anybody?  I realize I don't get much traffic from people researching SEO, but perhaps that could change.