Non-competes are basically unenforceable in California
Thats my understanding as well, which is why A123 sued in Massachusetts, and Apple tried (unsuccessfully) to move the case to California. According to Wikipedia the current applicable MA law states “A covenant not to compete is enforceable only if it is necessary to protect a legitimate business interest, reasonably limited in time and space, and consonant with the public interest”. The most recent test case I could find is IBM v. Papermaster (2009) involving (perhaps not coincidentally) Apple poaching. The court backed IBM and granted an injunction against Papermaster, citing and expanding "inevitable disclosure". Papermaster & Apple settled before trial, just like they did with A123.
Google, Microsoft, Apple and so on have all settled these cases in the last 10 years or so, so nothing has gone to trial so no case law has been established, but IBM v. Papermaster lays the groundwork for more enforcement of non-competes in some cases. IANAL but it seems the anecdotal assumption that "non-competes are basically unenforceable in xxx" may not be as absolute as we engineers assume it is.