For me personally, it's a matter of degree.

• I'm not going to buy a $2,000 set of speaker cables and I find the proposed science behind them to be rather dubious, but that dubious science at least retains a passing acquaintance with reality. The signal is what a cable is concerned with, and the cable does have to transmit that signal - what weird permutations are involved in carrying that signal have been and will continue to be open for debate among those who wish to debate it.
• Vibration isolation devices are similar - it's an extreme application of technology that already exists for vibration control (we use it on the fans and pumps we include in the HVAC systems I design every day) and I don't think the audible impact of such devices is possibly going to be appreciable. There are exceptions, of course: a co-worker recently got a DVR and found that its hard drive was transmitting vibrations into his cabinet and keeping his wife awake at night. He put some Mason isolators under the DVR and the noise ceased. In most cases the devices will at least functionally isolate vibration to at least some degree. Again, what impact that isolation may have can be debated among those who wish to debate it.
• CD pens just amuse me - they're pretty absurd, but at least they're attempting to directly interact with the signal path. It's not a very convincing attempt, but at least they considered offering some inkling of credibility.
• The Clever Little Clock (and its cohort jars of rocks or sheets of aluminum foil) doesn't even attempt to integrate into the signal path. It doesn't even have to be in the same room as the system (although apparently it does need to be inside the structure, since setting it outside causes it to cease to affect the system). It doesn't come in a package made from a single chunk of milled aluminum or hand-carved hardwood. It's a cheap, generic clock with a lithium battery inside and an orange sticker on the face. The rationales offered to justify it are purposefully vague and often contradictory. I'd feel better about saying that having my persian cat in the room improves sound because his mass and fur acts as a sort of moving acoustical treatment than saying that a battery powered clock sitting in a drawer of the end table has any effect on how my system sounds. Heck, I'd feel better say that having my cat in the house dampens the acoustical signature of the conventional foundation - it's still absurd, but at least I can point at a 20-pound cat sitting on the floor and say "mass, structural system, vibrations."

I say all this not to defend the dealers of other absurd "tweaks" - it's just that, at least for me, the CLC and its companion products are such an extreme and ludicrous exaggeration of the audio tweak concept as to offend on a whole separate level. Likewise, most of the other negative responses (and the humorous ones) come from like-minded folks who are in this forum because they are interested in the practical nuts and bolts of good home theater - we're not an audience prone to the tweaks you mention to begin with.

Is it a fraud? I'll leave that to legal experts to debate. Is it a concept so "out there" as to read like a parody (until you find out they actually take money in trade for their goods)? Oh, most definitely...