David wrote:

Being baptised has nothing to do with sin it is to do with becoming a member of the Christian family.

I'm a little amused by this idea that baptizing your child is "marking him." It's not like a tattoo or an innoculation. It's just a way to make the family part of the larger Christian family. My mother was somehow astonished that my brother converted to the Jewish faith, because, as she says, "He was baptized, you know." I reminded her that a little sprinkle of water (and as Protestants, it's not even "Holy Water") was not like being dipped in "Jew-be-gone" and even Achilles' mother forgot about the heel when he got dipped, so that sneaky "other religion" could still have snuck in (in addition to a poison arrow). I'm no sure she got the heel part, but finally acknowledged that at the age of 40, my brother was entitled to deterimine his own religious leanings. Baptism certainly didn't harm him, and the dozen or so years he spent going to church and Sunday school gave him a religous foundation that he could use as a basis of comparison for what he truly believed as an adult. 

Anyway, I would have a hard time coming up with three cons for adult baptism, unless you wanted cons on the entire Christian faith. The whole point of adult baptism is informed choice on the part of the adult, so as long as he or she is consenting to this, what is the problem? I suppose full immersion baptisms outdoors in January might have some cons...

There are some varieties of Christianity that don't baptise babies. they may well have a naming ceremony, but not a baptism. The 'Baptists' being one of these as they see it as a decision to be taken by the individual and only for 'believers'. Babies can't believe in anything.

From www.baptist.org.uk

Baptists believe that Baptism is for those who have come to faith in Christ and who are committed to living his way. In other words, baptism is for believers.

Membership
Many churches (often called ‘open membership churches’) will welcome into membership those who have been baptised as a small child, recognising that this baptism was a significant part of the person’s journey of faith. In some Baptist churches, however, membership is only available to those who have been baptised as a believer.
Leadership and Ministry
Most Baptist churches require all or most of their leaders (elders or deacons) to be baptised as a believer. In addition, the Baptist Union of Great Britain only accredits ministers who have been baptised as a believer.
Re-baptism
Because Baptists hold to the view that baptism is for believers, many churches will be willing to (re)baptise a person who has come to faith even if they were baptised as a small child. Some churches, however, will resist this out of respect for the practices of other denominations and the individuals on journey of faith.