Sneaky Ad Placement ?

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i've been receiving PTC emails for a few months now and haven't really had any problems with them (i like to think of them as my piggybank) anyways lately, about the last week or so, when i click on certain ads, another ad wil pop up (sneak in) behind the one i clcked on. they usually come from "circle of friends" or "adfusion" has this been happenning to anyone else? and do you think this is a sneaky tactic?