I was really quite disappointed about fountain hooks being removed - they were an extremely high skill, high risk high reward maneuver. It was also ridiculously fun to watch NaVi pull it off game after game in TI3 - part of what made that my favorite year for the spectator aspect of the tournament.
I honestly thought fountain hooks were a legitimate part of the game, until they were removed. They're hard to pull off. You could also sabotage your team by teleporting members with Wisp/Io to the enemy fountain. Ahh, the worst of times.
See also: 'FadeAway' grabs in League Of Legends. Very similar concept, amusing to ponder the ways in which the programmers made the same oversight: https://www.youtube.com/watch?v=WQp63SA-NZY (12s in)
Essentially, moving the target of the 'pull' while the pull is ongoing. Pudge->Fountain for DoTA, Blitz->Thresh for LoL.
They eventually patched it after a pro player abused it to turn a game around at the International 3[2]
It's a shame because 6 years later it's still one of the best moments I ever witnessed in the game.
[1]: https://dev.dota2.com/showthread.php?t=2989&p=11512&viewfull...
[2]https://www.youtube.com/watch?v=oB0tUrfDz6A