Do you phone hack or phone-hack?

On the Daily Mail editorial training course we have been discussing hyphens. It started with why two-year has to have a hyphen. That's easy, two is plural year is singular, so you can't have two-year without a hyphen. I was also always taught to use a hyphen to avoid ambiguity. Is a black cab driver someone who drives a black-cab, or some one who is black and drives a cab? A trickier question was whether phone-hacking should take a hyphen. A look through the papers and websites certainly shows inconsistency. The Guardian offers this guidance: Phone hacking - no hyphen for the noun, but hyphenated when used adjectivally, eg the PCC responded with its customary vigour to the phone-hacking scandal. 
That makes sense to me but will some readers just see it as inconsistency? The Mail's stylebook doesn't refer specifically to phone hacking but the preferred style is no hyphen at all. As a general rule if there is no ambiguity, then there is no need for a hyphen. But sometimes a noun (phone) and a verb (hacking) become such a familiar phrase that they become one word e.g. snowboarding. The discussion then led to the likes of fell-walking and road-running. Do they take hyphens, are they one word or do they have no hyphens at all? Has phone hacking become so common place that it has become a word in its own right? 
Anyway, hyphens are clearly important - and topical. They even led to this unlikely spat (thanks @subedited) between The Guardian and the Sunday Sport yesterday . 

I can't say bellend or bell-end is a word I have ever used in copy but, unusually, I am with the Sport on this one.

If you are interested in pursuing hyphens further, here's the advice from a selection of style books: 

MailOnline
You do not need to hyphenate adverbial compounds where the adverb ends in '‐ly’, such as 'The stylishly dressed man’. Use a hyphen only when the adverb does not end in '‐ly’, such as ‘the well‐dressed man.’
When the same form of words appears after the noun, hyphenate only if there is a chance that without a hyphen the meaning is not clear. Adjectivally – ‘multi-million‐pound house’, ‘make-up‐free star’, but ‘the star was make-up free’. 

The Guardian
Our style is to use one word wherever possible. Hyphens tend to clutter up text (particularly when the computer breaks already hyphenated words at the end of lines). This is a widespread trend in the language: "The transition from space to hyphen to close juxtaposition reflects the progressive institutionalisation of the compound," as Rodney Huddleston puts it, in his inimitable pithy style, in his Introduction to the Grammar of English.

Inventions, ideas and new concepts often begin life as two words, then become hyphenated, before finally becoming accepted as one word. Why wait? "Wire-less" and "down-stairs" were once hyphenated, and some old-fashioned souls still hyphenate e-mail.

Words such as chatroom, frontbench, gameplan, housebuyer and standup are all one word in our publications, as are thinktank (not a tank that thinks), longlist (not necessarily a long list) and shortlist (which need not be short).

There is no need to use hyphens with most compound adjectives, where the meaning is clear and unambiguous without: civil rights movement, financial services sector, work inspection powers, etc. Hyphens should, however, be used to form short compound adjectives, eg two-tonne vessel, three-year deal, 19th-century artist. Also use hyphens where not using one would be ambiguous, eg to distinguish "black-cab drivers come under attack" from "black cab-drivers come under attack". A missing hyphen in a review of Chekhov's Three Sisters led us to refer to "the servant abusing Natasha", rather than "the servant-abusing Natasha".

Do not use hyphens after adverbs ending in -ly, eg a hotly disputed penalty, a constantly evolving newspaper, genetically modified food, etc, but hyphens are needed with short and common adverbs, eg ever-forgiving family, much-loved character, well-established principle of style (note, however, that in the construction "the principles of style are well established" there is no need to hyphenate).

When an adverb can also be an adjective (eg hard), the hyphen is required to avoid ambiguity – it's not a hard, pressed person, but a hard-pressed one; an ill-prepared report, rather than an ill, prepared one.

Use a hyphen in verbs where necessary to stop this kind of thing happening:

Motorists
told: don't
panic buy
petrol

(While not panicking may well have been advisable, they had actually been told not to panic-buy.)

Prefixes such as macro, mega, micro, mini, multi, over, super and under rarely need hyphens: examples are listed separately. Follow Collins when a word or phrase is not listed

The Mirror
Avoid in verbs whose prefix is re, unless the verb begins with e or when the hyphen indicates a difference of meaning. Re-open, re-tested, re-structure, re-pay should be reopen, retested, restructure, repay. Re-educate, re-emphasise etc need a hyphen.
Un-named, un-known should be unnamed, unknown.
Never use hyphens in headlines and subdecks. If you need punctuation, a comma or dots will usually do.

The Irish Independent 

Use hyphens to avoid ambiguity or to form a single idea from two or more words. Use for:
Fractions: two-thirds, four-fifths, etc.
Most words that begin with anti, non and neo.
Any number used as an adjective - 10-hour, four-year-old boy, 15-man team.
Some titles: director-general, secretary-general,but not Attorney General, general secretary.
Compass quarters – south-west, north-east, etc.
Where a prefix vowel is followed by an identical vowel – re-elect, pre-empt, co-operate.
Compound adjectives, ie, when two or more words are used to modify a noun – eg, right-wing groups, balance-of payments difficulties. But when the adjectives follow the noun they describe, no hyphens are  needed – the right wing of the party, the State’s balance of payments.
Email does not take a hyphen.
–ly adverbs do not take hyphens, eg, it was a commonly observed phenomenon.
Some words have their meaning altered if hyphens are used. For instance, “recreation” is leisure activity, while “re-creation” means making something anew; “recover” means to get better, while “re-cover” is what you do with an old sofa.