lightning =/= sidechain. it doesn't entail a second blockchain. it's more of a delayed settlement mechanism.
every second layer solution comes with trade-offs, including sidechains. eg 3rd party trust (federated chains) or lower security (merge-mining). merge-mined sidechains can also adversely affect the mainchain in a tragedy of the commons scenario because,
as peter todd points out, they are effectively block size increases. in other words, it's a way miners can increase the block size without network consensus.
Interesting. For once, I've thought that the LN was a sidechain. But now I understand things more clearly. It's more of a delayed settlement system than anything else. After all, transactions are performed "off-chain" to be broadcasted to the Blockchain at a later time. Still though, I sometimes wonder the level of security of the LN as it used to experience a DDoS attack a couple of years ago. I guess that the LN sacrifices security over scalability/convenience for the end user (but at least it's better than increasing the block size on the Blockchain).
I'd imagine how sidechains will survive in the long run, especially when some rely on third parties. Blockstream's Liquid sidechain is known as a federated sidechain, which could be easily susceptible to external attacks. We need to eliminate the centralizing factor of the middleman if we want sidechains to work as intended. Even so, I believe that sidechains are rather unnecessary for the mainstream adoption of Bitcoin since Satoshi intended it to be used only as a financial system than anything else. Complicating things even more by implementing additional functionalities, would make matters worse.
Unfortunately, no. Sidechains are much less secure than Bitcoin.
With a federated sidechain, stealing all the bitcoins on the sidechain only requires collusion by 51% of trusted validators. With a drivechain, 51% of miners can collude to steal all funds on the sidechain.
That's certainly true, mate. Federated sidechains are a "no go" for the future of Bitcoin as a mainstream cryptocurrency for daily payments. They provide centralization above anything else. With centralization, comes security risks too. It's much easier to perform 51% attacks on these sidechains than on the main Bitcoin blockchain. I guess that sidechains are no useful other than serving as a private ledger for companies and businesses to do as they wish. People would prefer to deal with the main BTC blockchain than using any other alternative. Security/reliability/censorship-resistance goes above anything else. Over time, we'll be able to determine if sidechains are able to live up to the task or not. But I hardly doubt they'll be successful in the long term.