Whilst having online based friends is ok in principle, over reliance on communicating purely through technology does not improve social skills since you cannot see them and interact in a 'human' manner and you cannot hear tone of voice, see facial expressions and perceive body language etc etc
As for meeting them in real life, it's obviously good advice to put safety first. Always meet in a public place and don't allow them to know what street you live in for a while. If they are a genuinely good friend they will understand and respect your caution.