Couldn't find the thread where someone asked about this, but found a good example today.

Wow! That is pretty atypical mottling from what I have seen. Is that a typical leaf from that plant? 

i have seen that one one of my Tacoma Violet and Sucrette this year. i thought it was getting stressed from the sun. one on the TV is ready to drop. Sucrette leaf is still growing by it's getting more of those spots.

IMO, It looks more like a nutrient deficiency combined with possible sun scald.

I will second Pete,it does not look like FMV,to me.

Pete, I would be tempted to agree, but it only happens with some varieties, and they have been well fed this year, and last.

Where is Martin with his X-Ray specs?

An excess of one nutrient can have a similar effect as a deficiency in another.  In some cases it can cause deficiency in other nutrients.  For example, an excess of Phosphorus (as found in some bloom boosting fertilizer formulas) can cause a deficiency in iron and zinc.  Deficiency in either could have the effect in the picture.

I still think it would be a cool picture...

But I agree with James that it looks like chlorosis.

FMV tends to have mottled light green / dark green sometimes following the veins. Research has shown virus strains can result in the plant not "processing" the nutrients properly hence resulting in coloring effects simialr to improper use of fertilizer. When coupled with leaf deformadies, its most likley FMV.  Here is a picture of a red labanese about 6 months old with evidence of FMV.