You're not alone in your concerns about ETH (note why ETC even exists), although I don't personally expect any major transaction reversals to occur in the foreseeable future. People have other concerns, but the way that the big DAO incident was handled was definitely controversial, and those who believe in "decentralized" currency may have seen it as setting a poor precedent.
It's generally a wise tip to diversify, and never store more value in cryptocurrencies than you could accept losing. Apologies for this rather generic advice, but it really ends up being a personal decision. (If you're looking for someone to decide that for you, the speculation subforums are probably what you're looking for.
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