In some languages, it seems to have only affected interjections, and words commonly used as vocatives such as pronouns and kin terms.
Some languages avoid this by disallowing initial dropping if the result is a difficult cluster.
In Mbabaram for example, initial dropping doesn't occur if it results in a cluster other than nasal + stop.
When initial dropping occurred and the /ɡ ŋ/ were lost, the occurrence of [ɔ] was no longer predictable: it had become a phoneme /ɔ/, distinct from /a/.
When initial consonants were dropped and initial vowels shortened, the occurrence of the prestopped nasals was no longer predictable: Olgolo had innovated a series of prestopped nasal phonemes.