We all have seen some subpar performances in our day (maybe even played a few, I'm guilty) and you can't blame someone for wanting to get themselves on a stage some where "performing". In fact there are threads started once a month honoring these '"acts", or should I say dishonoring.
Poor performing bands are like bullets, completly harmless in the basement or garage under lock and key. But if you load them up and point them at a crowd of people, it can be harmful.
Something I hope we can all agree on is that these bands, whether they do or do not exist, wouldn't have had the opportunity to hurt our ears and taint our night, had someone not made the business decision to place them in front of us to do so. The blame really needs to go toward booking agents if you are starting to feel there are a lot of bands out there gigging that shouldn't be.
So who is doing it well? I say the Fine Line. I believe, along with great monitor mixes and expensive beer, they also tap all the great music that the cities has to offer and don't pigeon hole themselves to over booking one genre. The last few shows I've been to there have rocked and were packed. I put them at the top of my list of places I'm less likely to catch a crappy show on a Friday or Saturday.