There seems to be a wide-spread misconception that inactive accounts are some sort of strain on LJ's resources. They are not. Yes, they are taking up namespace, and they are taking up some storage space, but it is not the great hindrance on LJ's performance that people tend to think it is.
If an account hasn't been touched for a while, it is moved to the "inactive" cluster, to get it out of the way of active journals in the database, but it was still accessible and easy (invisibly easy) to re-activate if the user ever decided to return to the journal.
Active users who are using LJ are posting new entries, refreshing their friends page, leaving comments, and loading images. They're not just sitting there and quietly gathering dust on what's probably less than a gig worth of text. Storage these days, in amounts that the average person buys, is around $1/gig -- you can get a 200-gig hard drive for around $200.
The maximum entry size is 64k. That's not much when you're talking about image sizes, but that's a considerable amount of text. One of my friends has the collected works of Shakespeare in a file that's around 150 megabytes. In order for someone to have 1 gigabyte of storage used up by entries, they'd have to have 16,300-odd entries at the maximum entry size. Userpics and styles and assorted database overhead (entry titles, moods, music, etc.) would account for some more, but text really isn't that large to store. (I have 21,000-odd entries, accumulated over nearly six years now. I'm one of the edge cases. I still probably have under a gig of text stored, given that most of the entries wouldn't have hit 64k.)
Thinking about the $1/gig price range, and the fact that most users would have accounts under a gig, two virtual gifts would more than cover LJ's storage cost for each inactive user.