Please be advised I'm seriously short on sleep, so I'm likely to be cranky and less tactful than usual. That said:
You will get my phone number only when you pry my phone from my cold, lifeless hand.
You need my number because of "security issues"? The fact that I use your service for a publicly available blog rather indicates that I'm not too worried about security, at least for my on-line presence at this site. If my bank were asking, it would be a different story.
Facebook is fishing for a mobile number as well, though their particular ruse is one of "convenience". "It is sooooo much easier to post to Facebook if you are identified by your phone number, rather than that pesky login". And it's so much easier to get location data from the gps in the phone, as well.
In spite of my on-line presence, I value my privacy. Thus far, my phone is free from telemarketing and robo-calls. I'd like to keep it that way. My current location is my own business; I see no need to make it publicly available, nor to make it easy for miscreants to find an unoccupied home.
I'd appreciate it if you would stop asking. At the least, you could change your pitch to a more honest one: Hey, give us your phone number so we can make some extra money selling our lists!
No, thank you.