House Elf Magic

[milz]

No: HPFGUIDX 1671

How powerful are House Elves? Dobby was able to knock Mr. Malfoy down 
the stairs in Book 2 and Malfoy backed off when Dobby waved his 
finger at him. AND Dobby was able to apparate into Hogwarts in Book 2 
(which is something wizards and witches aren't able to do)! Then in 
Book 4, Winky was able to bind Crouch Jr. Also 
they perform magic without a wand.

Are House Elves more powerful than the wizarding folk and that's the 
reason why they are regulated? If they are powerful, then wouldn't it 
make sense for Voldemort to try to get the House Elves on his side?