I agree: it's a bit of anachronism at this point *but* as a cursory perusal of anecdotal evidence suggests, it isn't really much of a concern to the those that are actually paying for it (and some are quite vociferous about it to the point of accusing those that don't want to pay for it as being some sort of modern-day Scrooge, too cheap to pay Bob Cratchit for a service they deem as valuable as the air we breathe).
The really pertinent question is: does MS stand to gain anything by making it free? Will this actually increase the adoption of the 360? My take on it is no, it won't, as all those that are already paying for it don't mind forking over the cash for what they believe is a valuable service and those that aren't will never pay for it--it isn't as if there are many people thinking "oh to hell with the 360, I'm going to get a PS3 for many hundreds of dollars so that I don't have to pay for Live." In fact, I'd go so far as to say that the whole 'Live costs money so it's stupid/overpriced/blahblahblah' argument is nothing more than a bat for Sony and, to a lesser extent, Nintendo fans to beat MS fans with.
Furthermore, those that haven't bought a 360 yet aren't sitting on the sidelines waiting for the moment Live goes totally free to purchase the console as it probably doesn't factor into the though processes of most of the people that haven't bought one yet. More important to the people that haven't signed on yet are things like cost of the hardware and games.
So, in the end, does it make any sense for MS to give up on a revenue stream that isn't really going to matter to anyone one way or the other? Wouldn't it be better for them to keep charging for it so that that money could be used to help subsidize further price cuts, game development, improvements to Live, make the division more profitable (for those evil shareholders that care about such chicanery) etc?