Nicotine is one such compound. Nicotine is an addictive substance found in tobacco, eggplants, potatoes, cauliflower, and, according to one study, tea.
Nicotine addiction is partially responsible for cigarette addiction. In large doses, nicotine is very poisonous and can be fatal. A cigarette contains approximately 10 milligrams of nicotine. However, only one or two milligrams is inhaled directly when one smokes a cigarette, and only one milligram of nicotine is absorbed over the course of three hours of "passive smoking" (breathing secondhand smoke) in a room with minimal cigarette smoke. For comparison, one nicotine study found that ten grams of eggplant contains about one microgram of nicotine, while 19.2 grams of pureed tomatoes contains the same level of nicotine. (It takes 1000 micrograms to equal one milligram, so you'd need to eat ten kilograms / about 22 pounds of eggplant to take in as much nicotine as you'd get from three hours of minimal passive smoke.)
Scientific claims surrounding the levels of nicotine in tea range from negligible / nonexistent to 285 nanograms of nicotine per gram of tea in instant tea and 100 nanograms per gram black tea (whether regular or decaf). A 1999 study on nicotine in tea and vegetables stated that, "Nicotine content in tea leaves was found to be highly variable and sometimes much larger than in the Solanaceae fruits [such as eggplants, potatoes and tomatoes]." However, a more recent study of nicotine in food found no measurable nicotine in black tea purchased at a regular grocery store (likely teabags).
If the situation is as bad as the first study claims, then it would take over 3.5 kilograms (over 7.7 pounds) of instant tea (which had the highest levels of nicotine in the study) to yield one microgram of nicotine (the amount you'd get from minimal secondhand smoke).
If tea does contain nicotine, the levels are very low. It is generally agreed that these levels are not nearly high enough to impact cigarette consumption or cigarette cravings. Additionally, several scientists have pointed out that the absorption of nicotine through the lungs is very different from the absorption of nicotine through digestion. Therefore, the impact on your health as a smoker, non-smoker or former smoker should be negligible, and will likely be far outweighed by tea's many health benefits.
If you're still worried about getting addicted to the nicotine that may or may not be in tea, don't be -- you're far more likely to face caffeine addition (as well as sugar addiction if you add sugar to your tea) than you are to have any issues with nicotine in tea.