Think along these lines:

Exact match domain
Exact match URL
Exact match anchor text
Exact Match H1
Exact Match body.

All of these things that have traditionally been a signal to TELL Google what the page is about might be hurting now. To what degree, though, is anyone's guess. What type of web pages do you have? Are they set up like this?

That's when you have your KW appear too many times in too many places as it was said by "mosthost". Also can be very high KW density. Try to keep it around 1-3% percent, anything more Google might find it suspicious