Gingko and Coffee?

I have been reading some of these articles, and I would like to take gingko for better memory, and I have noticed a few times it is advised not to have coffee and gingko, is this the caffeine? Are caffinated teas, chocolate and cola drinks also discouraged? If not what about decaf? Also, is there any effects if taken with St. John's Wort?

Caffeine is a general stimulant, stimulating all body organs and increasing nervous and circulatory activity. It causes depletion of vitamins and minerals. An excess can cause anxiety, depression and a reduction of blood flow through the brain. Caffeine is not recommended when taking herbs, or in fact at any time, because it is thought to contribute to many ailments. You are right: the caffeine in teas, colas and chocolate has the same effect. Decaffeinated coffee is usually not recommended because it does contain some caffeine, because the chemicals used in the decaffeinating process may be harmful and because decaffeinated coffee, as well as regular coffee, promote acidity which may impede digestion and absorption of food and drugs.
Ginkgo is a circulatory stimulant. It increases blood flow to the brain, so is helpful to memory in cases where the blood flow to the brain is insufficient. In other cases, Ginkgo is not helpful for the memory, and may cause side effects such as headache. Coffee was likely advised against while taking Ginkgo because of its effect, largely caused by the high caffeine content, of stimulating brain circulation.
St. John's wort is often used as an anti-depressive or a sedative. Coffee directly opposes these actions.