It's hard to quantify what is secure and what is not. Actually working out what the incentives are for the system is surprisingly tricky, miners have all sorts of different motivations that conflict even when they would appear to be highly illogical on paper. Miners today include transactions with zero fees, where in a naive model of the network they probably wouldn't. The justification is often that it's financially sensible for them to do this because it inspires confidence in the system, making the price higher, which in turn makes their income higher.
The lack of possibility for a pricing feedback loop makes this all a little tricky too, as the system can't make any changes based on external influences.
> the potentially extraordinary Ethereum project, built to "decentralize the web" with its blockchain, which recently raised $15 million (in bitcoin, of course) by pre-selling its cryptocurrency prior to next year’s launch
I've still not met anybody who can tell me what Ethereum is without using the words "turing complete" (which it's not due the halting problem, just like Bitcoin). Most of the information you can get from secondary sources seems to just mirror Bitcoin (you can do this awesome thing, but you'll need an oracle to do it..).
The cost of securing the network doesn't really mirror the transaction volume. The effort is the same irrespective of the number of transactions in a block.
It's actually a lot cheaper to attack the network than you are stating, almost all mining uses Stratum which has been successfully redirected using BGP route hijacking in the past. It has no methods of authentication and does no way of integrity checking what it is mining against. A simple "mistake" in routing could have all of a countries hash power redirected to a malicious actor. You don't need power, datacenter or miners, a $5 wrench applied to the right head would do the trick just fine.
When you read this sort of document, keep a few things in mind that don't normally come across well from non technical authors. There is no such thing as "blockchain technology", that is, you can't separate the block chain from Bitcoin without making it hopelessly vulnerable to attack. The functionality and security of the system relies on the premise that miners are only mining due to the financial reward. If you don't a reward you don't have miners, you have a highly inefficient way of storing transactional data. As such, concepts that claim to take Bitcoin and turn it into Uber, Craigslist, eBay, messaging, twitter, video distribution, file storage are all complete nonsense spewed out by an author with little or no concept of the functioning of the network.
If anybody is claiming to take "block chain technology" and cram it into another system to make it decentralised, you ought to be showing them the door.
> Ripple disputes that they are affected, stating “All is fine and well with the Ripple protocol.
What Ripple/Stellar (same thing, different name) is a system which absolutely can not come to consensus under normal operational conditions. To solve this they have made the system entirely centralised, which isn't a problem for them but is for anybody who believes it to be decentralised. When you read things about Ripple know that there's two flavours: "Ripple", which is the original concept, and OpenCoin's "Ripple", which has a different technical underpinning. A lot of the early praise you'll see for Ripple was for the pre-OpenCoin version, which wasn't so heavily flawed as the one known today is.
I don't quite get why it's even mentioned in the parent article, it doesn't even have a block chain to begin with.
> using algorithms unsuitable for ASIC or GPU implementation
You don't want that. Give this a read.
https://download.wpsoftware.net/bitcoin/asic-faq.pdf