With all due respect Gary that doesn't explain anything. What problems? As an advertiser I never experiences any problems with my phone number being visible on my advert. I don't really care about other sites and I'm not on any other sites that do this. That might be for a reason? Unless you can explain what the problems are I still feel it is totally unnecessary and as clients often are limited with the amount of time they have to make their decision and gather relevant info, it could be the difference between making a call or having to leave the site without one.
I just noticed your explanation and I can't say I have had that problem and I don't remember this being up for discussion before?