Problems associated with excess use of tea?

Assuming you're talking about green/black tea, a problem I've become aware of is the caffiene. It's not a lot - green tea has about half the amount of caffiene that coffee does. However, drinking a lot of it makes my own heart skip beats. The skipping beats is not a problem, perse, as it's pretty harmless, but it's still annoying and irritating. Also, something in green tea can, when consumed in larger quantities, prevent proper iron absorption. If you'd like to read more about green tea, I recommend checking out this site: http://www.whfoods.org/genpage.php?tname=foodspice&dbid=146#safetyissues