I disagree. A project's errata is a very good indicator for the overall quality of the code and the team. If a database-systems history is littered with deadlock, data-corruption and data-loss bugs up to the present day then that's telling a story.
2) A few of the problems claimed are hard to verify
The particular bugs mentioned in an anonymous pastie may be hard to verify. However, the number of elaborate horror-stories from independent sources adds up.
3) New systems fails, especially if they are developed in the current NoSQL arena
Bullshit. You, personally, are demonstrating the opposite with redis which is about the same age as MongoDB (~2 years).
Apparently you have no idea how many critical bugs have been fixed in Redis...
When you strip MongoDB down to the parts that actually have a chance of working under load then you end up pretty close to a slow and unreliable version of redis.
Namely, Mongo demonstrably slows to a crawl when your working-set exceeds your available RAM. Thus both redis and mongo are to be considered in-memory databases whereas one of them is honest about it and the other not so much.
Likewise Mongo's advanced data structures demonstrably break down under load unless you craft your access pattern very carefully; i.e. growing records is a nono, atomic updates (transactions) are a huge headache, writes starve reads by design, the map-reduce impl halts the world, indexing halts the world, etc. etc.
My argument is that the feature disparity between mongo and redis stems mostly from the fact that Antirez has better judgement over what can be made work reliably and what can not. This is why redis clearly states its scope and limits on the tin and performs like a swiss watch within those bounds.
Mongo on the other hand promises the world and then degrades into a pile of rubble once you cross one of the various undocumented and poorly understood thresholds.
Thanks for that explanation. I agree that Mongo seems to have over-promised and under-delivered and that you do have to really craft your access pattern. I'm not a heavy MongoDB user, but from reading the docs and playing around, I was already under the impression that the performance of MongoDB is entirely up to me and that I would need a lot of understanding to get the beast working well at scale.
EDIT: zzzeek made a good point below about spending time in a low-key mode before really selling the huge feature-set, which convinced me, so I think you're right. I do like the idea of Mongo though, so hopefully they can get through it.