Sounds like these sidechains put a third party in control of your Bitcoins. It's interesting because it can be used to issue stocks and bonds paid with Bitcoin, but I think there will be losses most of the time, if not total loss of value due to the person in charge stealing or getting hacked.
That's why tvbcof was suggesting a seal of approval by the bitstream team, but this would require them eventually turning into an agency like group that goes through the code and evaluates it and to have a successful sidechain you would have to go through a third party and I am sure pay them and make any changes they mandate. Seems like way too many third parties involved for Bitcoin when it was supposed to be trustless.
Both of these comments are incorrect enough to make one suspicious that they are fairly blatant FUD of the synthetic kind, but I don't know that.
In the first case, there are technically possible ways for transactions to auto-revert. Thus, if one put a stake into a sidechain which simply vanished off the face of the earth it still might be possible to have one's Bitcoin come home. As always, if Bitcoin itself cannot be defended and is destroyed it won't matter very much. Interestingly, the sidechain guys (which has a very strong overlap with 'the Bitcoin guys') seem to have impressed a lot of people, myself included, with their progress on some of these fronts at this early phase of their existence.
To the second point, I would never use anything for anything important which I cannot compile myself. Everything is open-source and anyone can look at it. Blockstream currently consists of people who have a demonstrated disposition to 'getting off' on doing high quality security conscious software (as evidenced by a very significant fraction by lines-of-code in Bitcoin core itself not to mention some of the most critical of the support systems.)
I lack the skill and time to evaluate complex cryptographic code and perform system analysis and testing myself. I would value a solution which has been looked over by these people at this time. Long before Blockstream became some sort of and 'agency like group' I would have moved on to trusting others to provide this service for me.
