Luada, again we owe you a debt of gratitude. You do the work the rest of us are too lazy to do. Now I am beginning to understand why the verification process scales quadratic; not that me understanding matters per se but it is nice to know.
Example of such
transaction a can be seen here (from last year).
Holy cow!
now does this constitute a legitimate TX?
can't we just ignore this type of TX?
Depends; sorry. In a sense it is absolutely legit; it follows all of the rules. But it easily could have been coded less abusively.
Let's first look at a much more classic transaction
https://blockchain.info/tx/3a6a7d2456bfd6816ee1164e7c11307fa1c6855ee3116b6a1f8e6a14a98b04c4;address (amount)
12kDK8snhBD6waJ2NaMB7QvSf4DzMcE9ad (0.21963496 BTC - Output) {call it what you want; this is an input}
1FmUPrnZTBymMT3ktgMx61hQ3JRyWD7NPY - (Unspent) 0.14193496 BTC
13dhrUuUe2MrZsufYGAZnwnyE7k97FRZ1v - (Unspent) 0.0776 BTC
Nice and easy; one input, two outputs; classic.
Now compare that to the big one;
19MxhZPumMt9ntfszzCTPmWNQeh6j6QqP2 (Brainwallet - dog) (0.00001 BTC - Output)
19MxhZPumMt9ntfszzCTPmWNQeh6j6QqP2 (Brainwallet - dog) (0.00001 BTC - Output)
...
19MxhZPumMt9ntfszzCTPmWNQeh6j6QqP2 (Brainwallet - dog) (0.00001 BTC - Output) {this is the 1598 occurrence}
...
{followed by zillions of more inputs}
This could have been codes as;
19MxhZPumMt9ntfszzCTPmWNQeh6j6QqP2 (Brainwallet - dog) (0.01598 BTC - Output)
...
and saved 1597 inputs on this batch of inputs alone. Ok, sure, we could ignore this one; um, need to figure out how to recognize such without rejecting non-abusive transactions.