> YES is the simple answer. If only because giving an IP/cell number makes you look untrustworthy.
Where you are, do VoIP numbers look different to landline numbers? In the UK, most VoIP numbers are allocated in the landline number range. Of course it'll look odd if you live in London and present an Aberdeen number (or vice versa), but if your VoIP number is in your local area, then only the anally curious (or typical El Reg reader) will look up the phone company that allocated the number.
And, conversely, Stateside, mobile numbers are allocated from the area code blocks, so again, if your number has the right area code, it shouldn't look untoward.
> "What you can't afford a phone?"
Sure I can, but I *choose* not to be ripped off by the likes of BT.