He discusses the intimacy of the earliest Christian worship, explaining that Christians didn't meet in huge temples, but in people's homes. Even the homes of wealthier people could only accommodate 40-50 people, thus everyone had an intimacy with each other which probably exceeds what we have in today's church (excepting, of course, that which might be found in a vibrant small group).
Here is what he says about the holy kiss. Note my final comment after the quotation.
The simple exhortation to share the kiss, without any further explanation,
indicates that the gesture was quite broadly practised and familiar among the
first-century Christian groups. ...It is likely that the "holy kiss" or
"kiss of love" is to be understood as given and received in the worship
setting. Later references to the holy kiss in Christian writings of the
second and subsequent centuries consistently treat it as a liturgical action
[i.e., an act of worship], often linked specifically with the
Also, we learn that it was given mouth-to-mouth, an
exchanged kiss, expressing mutual intimacy and affection among all congregants,
and that for the first century or so at least, the kiss was exchanged with
members of one's own sex and the opposite sex as well.
from fears of impropriety and in efforts to abate pagan rumours of Christian
promiscuity, later church authorities sought to restrict the kissing to members
of one's own sex. Similarly motivated were rules that the holy kiss was to
be given with mouths closed and that no second kiss was permitted...! (At the
Origins of Christian Worship, 42-43).
Hurtado goes on to discuss the differences between the holy kiss of Christians and the socially accepted kiss in the Middle East.
It is not enough to say that their kiss was the same as our handshake. Today, we will shake hands with anyone and everyone, but the common kiss of the first century was more restricted. You just didn't kiss everyone.
The kiss was for intimates--one's own family and perhaps extended family. The kiss may be extended beyond this for greetings to express somewhat extraordinary honor. However, the NT kiss was different. It was shared between all the members of the fellowship, and done so as an act of worship.