Why do you say it like it's a bad thing? Isn't assaulting ghostly things the point?
The problem here is that the MM1 entry tells us that all spells will affect incorporeal creatures 100% of the time. The only thing they get to do is roll a 50/50 to ignore damage, unless it's one of those four kinds of damage described there...
So in other words, if I'm a cleric and there's a shadow here, I can cast cure light wounds and make a touch attack on a ghost, because this channels positive energy, and have a 100% chance to do some damage to him. this is something I have actually seen done in a low magic campaign when turning failed. Same goes if I cast an inflict spell and want to touch him to heal him, since it channels negative energy.
If a spell doesn't deal damage it still hits them. The entry clearly says even when hit by spells
they have a 50% chance to ignore damage. Says nothing about ignoring the effect, only the damage.
Thus if I web a ghost, he's entangled because it's a spell effect. Of course if I web the corridor in front of a ghost, he simply enters the wall and walks around it.
Enter Transdimensional Spell feat from Complete Arcane:
The last sentence of the "Normal" entry right under the feat benefit (the part that describes how things normally work so you can better understand the "benefit" you are getting) tells us that "There's a 50% chance that any spell other than a force effect fails against an incorporeal creature."
Well now not only can we no longer reliably web, sleet storm, glitterdust, or whatever the ghost... but now our clerics can no longer use their cures and inflicts on them because they are not force effects.
Consult the Rules Compendium:
Page 64, Incorporeality...
Rejoice! Sanity abounds:
Nondamaging effects affect incorporeal creatures normally unless such effects require corporeal targets to function (such as implosion) or they create a corporeal effect that incorporeal(Wow, we've been doing that one wrong... )
creatures are normally unaffected by (such as web or wall of stone).
There is even a little sidebar at the bottom where an author talks briefly about the mage spell Ghostform and what it grants the caster in terms of becoming incorporeal, like whether he can still be dominated, or gain the benefit of the bard's Greater Heroism. It was here that he said the line above was added to the Incorporeal definition in Monster Manual III.
So we can conclude a few things from these various definitions:
-Since the Monster Manual is the primary source, positive/negative energy attacks, force effects, and ghost touch weapons all affect incorporeal things normally. The complete arcane "normal", as a secondary source that contradicts a primary, is summarily ignored.
-All other spells that deal damage have a 50% chance to not deal their damage against an incorporeal target
-Spells that specifically call out that they effect incorporeal targets or reach across planes also affect incorporeal targets normally
-All spell effects that require something corporeal to function AND do not call out that they effect incorporeal things fail 100% of the time
Now the Transdimensional Spell feat:
"A spell has it's full normal effect on an incorporeal target..."
A web would normally affect an incorporeal target, but fails because he can walk through it.
A Shards of Ice spell would have a 50/50 shot to deal it's ice damage, but have no effect on the ghost's speed because he can pass through them.
Transdimensional Spell breaks that last rule and allows a spell to have it's full normal effect on an incorporeal target. In a fashion, it causes the spell prepared this way to now call out that it affects incorporeal targets.
To interpret it any other way would have it do nothing. Even a lightning bolt prepared as a Transdimensional to have it's "full normal effect" would simply cause the DM to pick up the dice and roll the "normal" 50% ignore damage chance.