Here is the analysis of Anonymint on the weaknesses of Zerocash/Zerocoin. For those of you who are new and dont know him. Anonymint is a "world class programmer who knows his sh*t" and even though he is not part of the dev team have been instrumental to the discussions leading to the development of the latest Darksend. This is worth reading.
I hope readers find my posts helpful?
ZeroCash is going public in a few months time ~20 May. Regardless of whether they have anything tangible or just a published paper,
I don't think they will have beta-test level code then.
This is about not being drowned out and then being considered a clone.
No way Darkcoin can be considered a clone, as Zerocash completely hides the payer, payee, and the amount of transactions. The block chain is a complete fog. Zerocoin doesn't do this.
Zerocash will have some positive spin. They will talk about e-cash and anonymity.
They will make the point I just wrote above.
What they won't talk about are the problems with the project.
The main weakness of Zerocash is it adds an additional 3 minutes between check out and completion of payment. (Add that on top of Bitcoin's 10 - 60 minutes, or Litecoins 2.5 - 15 minutes). Zerocoin doesn't have this problem.
The main weakness of Zerocash and Zerocoin are they depend on new crypto which hasn't been subjected to years of cryptanalysis, and if you put it on the block chain, then it is later cracked, the entire coin is potentially F.U.B.A.R..
Whereas Darksends are offchain! Even if you crack the crypto of Darksend (which uses very old well vetted crypto), the block chain remains uncracked!
The other weakness of Zerocash and Zerocoin is they depend on a trusted party to create the master parameters. If anyone retains that information (even if they snooped it using the NSA's air gap detection mechanisms), they in the case of Zerocash they can create unlimited coins and nobody will even know it! In other words, the coin supply becomes unknowable!! I am not exaggerating!!
Another counter point may be that each Zerocash transaction takes 9ms to verify (500ms for Zerocoin). Thus they can only put 111 transactions in a block per second per core of the CPU on the miner. Visa does 2,000 - 4,000 transactions per second, so for Zerocash to scale to global transactions needs 40 CPU cores per miner (e.g. 10 iCore i7 CPUs), not including denial-of-service transaction spam. Transaction spam could be really bad if they don't have a transaction fee or other means to control it. Any way, 40 CPU cores is not really a big problem if mining will be done only in pools.
But crypto-currencies are hoping to enable microtransactions, thus the transactions per second would explode by orders-of-magnitude.
Thus appears to me Zerocash is incompatible with microtransactions unless mining becomes very centralized among a few powerful pools.
Centralization of mining is a severe problem with Bitcoin having
onetwo or three pool with 51% of the hash power now.
hi hi thnx you did anyway.... 
but ppl mine it anyway... need of some vision and here we go...
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