I would point out though that this argument is against a designer with "human-like" qualities or that would design things like humans do, not against any designer. I don't even think it disqualifies the potential designer as incompetent. Sure we can look at a lot of "design flaws" in living things, but it may be that we just don't see the purpose for a particular design - that is, it doesn't fit our human qualifications as a "good" design.
What your argument does really well is it shows that using human designed objects and recognizing that they are actually designed does nothing to address design in nature. They do not have the same qualities at all.
It goes way beyond that. There was a discussion on phylogenetics a few months ago where it discussed the calculations involved. There is an equation you use to figure out how many trees are possible given the number of characteristics you are sorting. As it turns out, for 30 characteristics there is an astonishing 10^38 possible trees.
"So, how well do phylogenetic trees from morphological studies match the trees made from independent molecular studies? There are over 1038 different possible ways to arrange the 30 major taxa represented in Figure 1 into a phylogenetic tree (see Table 1.3.1; Felsenstein 1982; Li 1997, p. 102). In spite of these odds, the relationships given in Figure 1, as determined from morphological characters, are completely congruent with the relationships determined independently from cytochrome c molecular studies (for consensus phylogenies from pre-molecular studies see Carter 1954, Figure 1, p. 13; Dodson 1960, Figures 43, p. 125, and Figure 50, p. 150; Osborn 1918, Figure 42, p. 161; Haeckel 1898, p. 55; Gregory 1951, Fig. opposite title page; for phylogenies from the early cytochrome c studies see McLaughlin and Dayhoff 1973; Dickerson and Timkovich 1975, pp. 438-439). "
29+ Evidences for Macroevolution: Part 1
So out of the 1x10^38 possible combinations of DNA bases for cytochrome c that a designer could have chosen (reminding you again that cytochrome c has nothing to do with morphology), the designer just happened to pick the 1 combination of similarities and differences that evolution would produce? That doesn't add up.
No designer would spend the massive amounts of extra effort and time just to make designs fall into the pattern that evolution would produce when there is zero reason to do so with respect to function. It makes no sense.
Edited by Taq, : No reason given.