It's quite useful information in the Chromakey field
The VHS Oversampling idea is also a trick that can be used very successfully with chromakeying. I have done this one a few times with grainy bluescreen or greenscreen footage and it makes the difference between rescuing the chromakeying of the footage or trashing it and starting again...
1) take the footage into SE and separate it from it's audio.
2) slow it down to 50%
3) make a duplicate of the slow clip and put it right below on the time line (holding down the v key for vertical alignment)
4) select the lower clip & press Ctrl+> to move the lower clip one frame to the right.
5) press f8 & set alpha to 128 for the lower clip, and press y on the clip to make it overlay enabled.
6) if you play the clip and look at it you will notice that you have now blurred one field into the next. This gives a slightly mushy motion to the video, but is serves a great deal to average out the differences between pixel brightnesses and thus it dramatically reduces grainyness and frame to frame jitter of chromakey edges. If you are willing to make a sacrifice of a bit of quality, you can also apply a minor blur to one or both of the layers (experiment with small numbers on this one, a little goes a long way but too much will hurt your clip), which also serves to remove grain by averaging neighboring pixels.
7) render the clip, at 200%, which will restore it to it's original speed, then check it out.
A note on focus blur, vertical blur is more effective for most codecs because codecs often use rectangular pixels for color information. Vertical blurring will smudge the chromas of 3 lines into one line. If you used horizontal blurring you would have to blur about 5 pixels wide to get the same or similar effect with rectangular chroma pixel codecs. For more info on this, check into the definitions of '4:2:2' and other similar ratios.
You can also get into the nuances of blurring individual channels if you want to and seeing how green channel blurring or blue channel blurring affects your chromakey's algorithm.
If you want to go really wild, blur the hell out of your clip and paste it over the original, make it very transparent to only influence the colors a bit, and render it again. Then see what you get.