Users aren't changing defaults on fidelity bonds (or anything else for that matter) 99% of the time. There have been a lot of improvements since 0.9.0. That is why I said someone should fork it, remove fidelity bond stuff or change all defaults, and let people run it that way.

I also remember JM before FB, and yes people might make multiple offers on the same coins but it's not a problem. They can't fulfill the taker without all the coins they claim to have so they'll get dropped from the join and they don't learn anything about your utxos (IIRC).

The sybil problem might also be solved enough for practical use by simply increasing the default number for makercount. But users have always been encouraged to do multiple joins spread out over random times in part to avoid sybils anyway.

I think many people would accept this trade off in order to get paid for coinjoining.