The size of political parties and pressure groups gives them more power in Interactive Democracy, should the leadership be able to persuade their members to vote in unison. This may be accomplished quite powerfully by emailing their members to advise/persuade them on how to vote.
Is this a bad thing?
I don't think so. Party leaders have little real power over how their members vote, except by persuasion. (Votes are cast in secret, so the leadership should never know how individual members are voting.)
However, this poses a potential problem for the introduction of Interactive Democracy because those parties with smaller numbers of members, but many seats in the House of Commons, may use their political power to oppose it. That is to say, they may prefer to hold on to power rather than make democracy more democratic!
(The above graph is shown here, in an article about BNP membership.)