Mmm. Yes, it's a tricky one. I'm generally against any positive discrimination anywhere in favour of particular groups unless you believe that a key function of the institution or operation performing the discrimination ought to be social engineering, and that that should take precedence over other things. If not, then you want to be fair and representative, but not artificially biased. We could debate whether it's the role of conferences to perform social engineering. The organisers of the conference may well decide that it's part of their motivation, but, as you point out, it's difficult for anybody from the outside to come in and impose their particular preferences. Yours may be gender, but how many other under-represented groups should be taken into account? With these things I think it's always a good thought experiment to think about whether you'd be similarly balanced the other way. If you were going to conferences in the fashion, or publishing, or nursing, or primary-school-teaching worlds, for example, which were substantially female, would you make the same complaint if they had insufficient male speakers? A friend was recently invited to a women's dinner for the female lecturers in her university faculty here in Cambridge. She declined. "Can you imagine", she said, "what people would say if an invitation went round for a men-only dinner?"