Fire is your friend. It helps you cook, it makes your house warm in the fireplace, it wards off angry spouses.
However, if you play with fire, you get burned.
Lag is the exact same way. Just like if you throw gasoline on the fire to create a bigger fire on your stove, barbecue or fireplace, it is going to run out of control. If you try to create more lag than you can control, you are going to get burned.
Natural lag, like fire, is your friend. False lag, is gasoline on the fire.
Ah, but centrifugal force is your friend too and trying to add or hold false lag, ruins the aid centrifugal force gives you in squaring the club and speeding it up..
The videos get a bit more technical than I like to get, but there is a large technically oriented crowd right now in golf. There are two videos, watch both parts.
EDITED: I thought I would post another video illustrating what I am talking about from a great player. The video is after my two and it is one of my favorite swings. Notice the release from the top in sync with the turn…and no excess forced lag.