I've had betas who tacitly bailed -- that is, never got back to me. These were always people I only knew through the Webz. Peoples who have to look you in the eye every now and then will probably have to come up with an excuse eventually.
My BFF is my bestest beta, and has been for more than thirty years. And I'm hers. And my agent is a great beta, too, and always responds quickly.
I used to beta a lot, but no time for more than a quick SYW pass these days. I've had people who never responded to a detailed crit. Not cool, IMO -- I spent hours, and you can't cough out two words, like, um, thank you? If I do start beta-reading again, I will need to have a better knowledge of that person and his writing before I say yes.
Neophytes prone to elementary errors need either a super-patient mentor or a shelf of good books to study and compare to their own work. Things like bunged up dialogue punctuation, you should be able to correct by simple observation. What pro-published books are you reading that do anything like this:
"I'm going to bed." She said. "Okay." He replied. Oh, and take the hedgehogs with you. he added.