For follow-up discussion and general commentary on the topic. Comments are sorted chronologically.
The Altar call may be just a means of expressing what is going on in the heart, so not essential; it also carries the risk of the individual who bases his faith on "having gone forward" rather than on the Lord.
But despite all that, the danger of lethargy that can set into the church when a call to a positive response is absent is great: We suffer terribly from it in the churches in the UK.
Put simply - No requirement to respond leads to no expectation of a response. No expectation of a response leads to no faith that God WILL change lives - and it's only a small step to going through religious motions and expecting and seeing no move of God on peoples hearts. With some wonderful exceptions, tyhis is the church in the UK. We need God to move! Keep calling for a response!