Lady Amanda, your question is intriguing.

However, the answer lies completely in one of the most central underlying foundations of BDSM. ~TRUST~

When One is seperated from a naughty sub, You must, as you suggested give them unpleasant assignments. What those are depend upon those in the relationship and are realy unimportant. What is important is having the trust in your sub, that he/she will complete the assignment and keep to any limitations you place upon them.

This trust goes both ways, though, the naughty sub (most naughty subs actualy want to be pnished to bing them closer to You). THe naughty sub must have teh trust in you that you will follow through and check his/her progress and completion. The sub must also know that You will place further strictures and punishments upon him/her for failure to complete the punishment task(s).

Though not nearly as satisfactory as skin to skin, RT physicla punihments they can work when life and distance seperate the ofending subby from the tail of the lash, it can be effective, ~if~ the trust in one another is there. This can be applied to on-line as well as seperation due to the strangeness of life.

I am strictly opposed to any kind of removing yourself from your submissive as a form of punishment. I see that as selfish and abusive, and completely non-constructive. Personal opinion of course, but I did once see a submissive who was punished by being deprived of her Dominant and she was a trainwreck because of it, and this formed My less than humble opinion. But then her Dumbinant was not really a Dominant anyway so.. :P