(Also, Jude says that the angels who left their former abode were locked into the "abyss"... I personally think that would be quite a deterrent for future occurrences of this happening.
Jud 1:6 And the angels which kept not their first estate, but left their own habitation, he hath reserved in everlasting chains under darkness unto the judgment of the great day.
Jud 1:7 Even as Sodom and Gomorrah, and the cities about them in like manner, giving themselves over to fornication, and going after strange flesh, are set forth for an example, suffering the vengeance of eternal fire.)
The Book of Enoch makes refrence to this that the Angels who left Heaven and made wives out of the daughters of men were immeditly cast into the Lake of Fire.
Were as the Angels and marriage doesn't it say the Angels in Heaven Mark 12:25 does this apply to the Fallen Angels on Earth. We know that Hebrew 1:14 could not apply to the Fallen Angels and Mark 12:25 specificly states the Angels in Heaven. I would asume it is because the Angels in Heaven are Obeying God were as the Fallen are not.
As far as Angels being given in