I knew Gingivitis would draw up a list of possible options, saving me the trouble.
My personal experience is that Drain is not necessary for spells, any more so than guns need to track ammo. I find that spellcasting is well balanced with other offensive options and does not need to be curbed. I haven't run into trouble with casters abusing non-offensive spells either.
Spirits are a different matter. Currently there is no mechanical limit to summoning and resummoning, either to land the biggest spirit possible or to spam the opposition with hordes of cannon fodder. Not only are they infinite, but spirits don't even require Shadow Amps like drones do. Furthermore, summoned spirits are not limited by the number of services - their only duration is sunrise or sunset - so that a summoner in the party is perpetually doubled in strength. (Or, rather more than doubled, as spirits are tremendously powerful.)
One table I talked to used a version of Glitch Swapping that Gingivitis described. For each service that a spirit provided, a number of Glitch dice would be rolled equal to the spirit's level. (1 die for a Lesser spirit, 2 dice for a normal spirit, 3 dice for a Greater spirit.) The number of 1s would be the amount of drain incurred. Thus the odds of a Lesser spirit generating Drain for any given action would be low (17%) while a Greater spirit would be rather likely to generate a least a box of Stun (42% chance of at least one 1.)
I haven't played with this rule personally, but I like the way that it scaled the risk and created some opportunity for Lesser spirits to play a meaningful role. I also like how the Drain roll per action (rather than per summoning) curbs the motivation to have spirits perpetually hanging around to do everything for you.
I believe I also talked to a table that was much more vigilant about treating spirits as independent NPCs, to the point where they could only be given specific instructions (that would have to be followed) by spending Plot Points. The Plot Points effectively served as the spirit's services. That's a different approach than Drain, but was another viable approach to prevent spirits from dominating the action.
I know those are anecdotal, but I hope it provides some food for thought.