Generally a bitcoin transaction is considered assured after 6 confirmations.
They say an NXT transaction needs 10 confirmations.
How many confirmations needs a NEM transaction to be pratically irreversible?
Those "pratically irreversible after x confirmation" statements are kind of arbitrary. But if you want a statement like that I would say that since NEM is somewhat similar to nxt it will need 10 confirmations too. But that's only true if there is no severe bug inside the code 
I'm actually interested to hear what a dev has to say about this as well. Does the Eigentrust++ algorithm used to determine the trust level of peers help NEM in this area?
I'm actually interested to hear what a dev has to say about this as well. Does the Eigentrust++ algorithm used to determine the trust level of peers help NEM in this area?
Bloody is a dev :)
From what i understand Eigentrust++ does not help in that area as it has nothing todo with the confirmation process.
@amytheplanarshift:
No, Eigentrust++ doesn not help in that area. Eigentrust++ helps when selecting nodes to get data from, i.e. a node doesn't want to download a lot of blocks from another node and verify those blocks just to discover it got fooled by a malicious node. That would waste processing power. But if a malicious node really has a better chain then this chain will slip into the network after some time even with Eigentrust++.
In a normal situation (there is no attack from some evil nodes underway) the forks in the network should be not deeper than 5 blocks. So 10 blocks should be considered as "safe". But if an attacker somehow succeeds to block/slow down the propagation of the data in the network, the forks could be deeper.
When I check the pre-trusted nodes in the network, usually a deviation of 3 blocks indicates trouble.
Oh, sorry lol it's hard to keep track! Thanks for the clarification about Eigentrust++, it makes more sense now. 
In a normal situation (there is no attack from some evil nodes underway) the forks in the network should be not deeper than 5 blocks. So 10 blocks should be considered as "safe". But if an attacker somehow succeeds to block/slow down the propagation of the data in the network, the forks could be deeper.
When I check the pre-trusted nodes in the network, usually a deviation of 3 blocks indicates trouble.
It would be nice having the blockchain explorer (or other site) showing an extimation of current forks depth.
It should some nodes and calculate differences in last blocks... is it feasible?
We are planning some view where you can check how a node is doing. But the exact way it will look is not yet cemented.