Felicity Dale answers this oft asked question about simple/house/organic churches: Aren't house churches susceptible to heresy and false teaching without a trained clergyman to protect them?
For some reason people seem to think that a hierarchical institutional church is some sort of defense against heresy but you don't have to look very hard to see that is not true (see: Protestantism, Mainline). Check out her answers in her post Heresy in the house (church) . I agree with her, the best defense against heresy is a body of believers that are equipped and empowered to study the Scriptures for themselves and who are willing to raise their hand and ask questions when something they hear sounds squirrelly.
Another point to make is that when people ask about "heresy" I wonder what they really mean. Denying the trinity? Rejecting justification by faith alone? Or is it more likely a disagreement on a secondary issue that doesn't rise to the level of heresy by any rational or reasonable measure. I think we are a) too soft on actual heresy in the church and b) too likely to label something heresy that doesn't rise to that level.