There's really no incentive to take multiple short rests--if you have that much time to spare, why not just take a full rest and make everyone happy?
Can anyone give an actual example of a situation where this could be abused?
There is a big disincentive to taking a long rest instead of multiple short ones : you can only take one long rest per 24 hour period. You could take several 3-hour breaks in between action and the fighter could have 100% HP at the start of each battle, without even spending a single HD.
In my group's campaign it can be and will be. We have these things called way portals where we can rest between exploring the world. The most you can rest is a long rest, but also several short ones, in complete safety. This we have done also in the forest, so it's not inconceivable that we could benefit from surgeless healing on our fighter multiple times.
Put it this way. As a ranger, I have very limited healing in my Cure Wounds spells. I have cast it before on my own character, and the fighter and sometimes the rogue. If the fighter I never have to heal with Cure Wounds so long as the group takes 2 or 3 hours in between pushing forward, we can and will do that. It would be stupid not to. Not cheesy to do that, it would be mechanically stupid to enter combat and waste valuable daily spells that we might need later when we
can't take those 3 hour rests.
Telling DMs to railroad adventurers is not a solution to this. It's systemic. We reported this issue in the playtests
and they fixed it. And then
un-fixed it. And now they're telling people that they play cheesy if they don't want to waste their character's daily resources when they don't have to, namely when their characters aren't being pursued (which happens, just not every time, all the time, which would be the truly cheesy thing and would cause all our players to quit if our DM did that to us to push us along).
Free surgeless healing, how could that be abused? Seriously? Man, you can't played D&D that much. We play in a VERY gritty high stakes campaign and every single spell and HD is treated as the precious little flower that it is. If we
can benefit from the fighter healing himself for free by taking an extra hour while we wait, we
will do that. And so should
any smart group that is trying to survive against tough odds.
Put it this way, we fought a wyvern at level 1 (with a little help). We are up against an army of ogres with ogre magi chasing us, who are trying to awaken a terrasque. You must be kidding me if you think we wouldn't let our fighter heal up to preserve my cure wounds spells and his HD. The next time we get to rest we might only have the chance to rest for one hour, and spending HD needlessly the day before isn't a good option either, because you only get back half your HD the next morning. You are aware of that, aren't you? Have you played D&D Next at all? HD are precious, don't waste them, and don't spend them if you don't have to. Which, for a fighter, is never so long as you can rest a couple hours instead of for one hour.
Imagine Mike Mearls coming in to watch our gritty game here, and telling us we're playing the game wrong because I didn't want to waste my few cure wounds spells on the fighter when I could save it for myself or the rogue or the party wizard instead. It's baffling to me that that type of specious argument carries weight around here. It's an invalid one, as I've just shown in a real game example.