What Goes into Anthology Editing? What Should You Be Aware of?

Sometime in the next week or so I'll post some thoughts on editing anthologies.But I thought it would be interesting to get some feedback from readers first, in answer to any or all of the following questions. You can note whether you're referring to original or reprint anthologies if that's important for context.(1) What do you personally look for in a fiction anthology?(2) What do you feel are the top five constraints on anthology editors when putting together an antho?(3) What do you think is the toughest part of putting together an anthology?(4) Do you think it's easier or tougher to edit an antho now than, say, 20 years ago?(5) Do theme anthologies attract you more than general fiction anthos?(6) If you were able to edit an anthology, what would be your dream project? (You can be vague if you like.)Feel free to add any general observations, too.I'd prefer it if existing anthology editors didn't respond to these questions. I'm interested in responses from non-editors.