On page 372 as Slothrop becomes Rocketman, Pynchon writes that "names by themselves may be empty, but the act of naming..." (372). Pynchon doesn't exactly finish the thought yet if we infer him to mean that the act of naming is very significant (meaningful, whatever you'd like to call it) it raises a lot of questions about Slothrop's name and his identity. In part three we see him as Ian Scuffling, Rocketman, Max Schlepzig, and Plechazunga. Yet in the ones we have seen thus far in the reading (as of pg. 400 we have only gotten as far as Rocketman) there never seems to be much story behind the name changes. Ian Scuffling is a character without a story in many respects, he is simply an alias to allow Slothrop to hide and travel. Rocketman emerges from a hash induced haze and is never entirely explained. What is it in the act of naming that gives it meaning and what can we take from the constant name changes? What is the meaning in the act of naming and how has that played out so far?
This is another of those binary subjects in Pynchon: does an object (or person) retain its identity despite the name it is given (so the act of naming has no significance) or does the name somehow change the object in question? Pynchon seems to be making a case for the latter, which relates back to linguistic relativity (the language one speaks determines how one thinks). It's interesting too because Pynchon obviously put so much thought into the names of his characters: allusions and puns abound. He obviously expects us to consider his characters differently as they have different names...do we? As Rocketman Slothrop does seem to be a bit more of a comic-book character, and he is a little harder to take seriously. Also he himself seems to change a little in each of his avatars to fit it more precisely: by treating him like Rocketman Saure and the others manage to convince Slothrop to steal the hash from the White House, though it may not have been something he would have done as Tyrone.
I'm not sure how this fits precisely into the previous two posts, but I think it's worth mentioning that re-naming has a ritual, and almost cathartic, element in Genesis. Yahweh (the god of the Hebrew Bible) renames Abram "Abraham" after blessing him with His covenant; Abraham's wife's name, too, changes from Sarai to Sarah. Pynchon seems to almost be playing with this trope in the form of disguises and aliases. The point raised above about whether or a person retains her identity in light of a name change is a good one. In Slothrop's case at least, not a whole lot seems to change for him existentially (in terms of paranoia and what not) as he appropriates new identities.
I think Pynchon plays with names/identity a lot in the book in order to emphasize their ambiguity. Weissman and Blicero are the same person, for example, and yet go by different names and have very different personalities. There's also Polker's daughter, who returns to visit him every year. While she still calls herself "Ilse" he begins to suspect it's a different girl every year, and wonders if he knows her at all. There's huge confusion in naming in GR, presumably related to identity and obscurity.