I disagree, but then again being the owner of several domain hacks I would wouldn't I.
Firstly there are two main kind of hacks:
1) Where the suffix is part of a word of domain site, examples would be 'li.st', 'Tex.as', 'fla.me'
2) Where the suffix is a meaningful and relevant word in its own right, here examples would be, 'love.me', 'help.us', 'fly.to'
Both the subsets above are hacks, some prefer one type over the other, and others like Adam think they are all worthless without a huge budget for marketing, and even then question their value.
The strongest dislikers of hacks are of course those that say the .com is the only type of domain worth anything, but then again I guess they would walk past a hundred dollar bill on the floor if they thought they might stand a chance of getting a thousand dollar bill by not picking up the hundred. Strangely enough hacks seem to be doing OK on the aftermarket, especially when you consider just how few of them there are, but as always it is a case of matching seller and buyer, as it is with any domain - and that is not always easy, but the great thing for hack domain owners is that they can hold out as their domains are literally unique.
Downside is that a developer will have to know how to market the hack domain website. The other downside is that many established businesses are yet to realise the uniqueness of a hack, especially with the old guard of nay-sayers saying they are worthless. But slowly the number of hack sales rise and they continue to increase in value generally. The upside will be when an advertising agency suddenly realises the visual impact a hack can have and runs with one, then we will see hack values shoot skywards. It is indeed surprising just how backward looking some of the industry is, never seeing that our industry is constantly evolving and refusing to evolve with it.
NB. (I would just like to say that I do not own, have owned, or have any connection in any way with any of the domains I have used as examples.)