Since November 2006, you have been able to sign e-petitions to the Prime Minister here; you may also create your own e-petition.
2,980 petitions are accepting signatures on 14th February 2007. 2,089,438 votes have been cast for these petitions, implying that the "average" (mean) petition has 701 votes.
However, the votes are distributed very unevenly: 88% of the votes are cast for 2% of the petitions, and one petition has attracted more than half the votes. Less than 5% of the petitions are "above average". The median petition has only 15 votes.
What conclusions can be drawn? It might be possible to please most of the voters; but it is a waste of effort trying to please most of the petition writers: the majority of petitions have so little support that they do not deserve political attention.
This appears to support the style of government that we already have. Large numbers of votes do count; but the average petition will be fobbed off with nothing more than a polite letter. The only thing that will change is that now you will be fobbed off with a polite email - and maybe follow-up emails from Number 10, for the rest of your life. Such is the march of technology.