Correct. It depends on the combination of words used. If you are starting a bank, bank.com would be more valuable to you than banks.com.
i dont agree with you. i have some 2 words domains and all of them are easy to remember and they are getting good visitors
Depends on the application. HauntForuml.com is for a haunt forum. HauntForums.com can be a directory of haunt forums. Just a general example but you get the idea. I have great singular and plural names. Dracubat
It does depend on the term. Sometimes its better for singular: i.e. sugar.com vs. sugars.com Sometimes its better in the plural: i.e. shoes.com vs. shoe.com Sometimes it doesn't matter: hat.com vs. hats.com Skinny
I would say that it really depends on the name. I've seen single words that sell for more than the plural & vice versa. Casino.com is worth more than Casinos.com Loans.com is worth more than Loan.com