Poll Validity - CallerID w/Privacy Plus bigger factor than Cell Phones?

[NAO]

I've seen much hubub about cell phones in polls and the fact that some people have only cell phones, etc.

I have both cell and land line phones, but both have CallerID and my land line has Privacy Plus (forces blocked callers to identify). In my circle of people, these are MUST HAVE services.

I'm sure that this is why I've never been polled. It gets blocked if it shows up as "unavailable" or "unknown" and if a call shows up as out of my area code, and I don't know who it's from, I just ignore it. If it's important, they can leave a message. I suspect that this is typical call screening procedure for many.

How would Caller ID, Privacy Plus, and SOP screening of unknown calls affect polling validity?