Generally speaking, no.
Too much of anything is bad for you, even too much water intake can cause death.
Under normal reasonable circumstances, Tea is not bad for your health. In fact, in moderation tea is very healthy. There are plenty of studies done on the link between a decrease in cancer and green tea, refer to .
Black tea is a whole other matter. Too much black tea has been showed to tax the kidneys. In some rare cases, black tea has caused organ failure and death. Those cases have been sensationalized, are rare, and other factors are involved, such as a pre-existing condition.