High Speed Rail
The answer for every program is "compared to what?".... you could do all these other thing: desalinated clean water, more sewage treatment, much more clean energy, and 3,000 miles of more lanes and 9,000 miles of resurfacing.... or a high speed rail that few will use. Which sounds better? So it's not that I don't like the idea of High Speed Rail, it's just my brain won't let me stop comparing how much good I could do with the money, if we didn't waste it on this boondoggle.
In 2008 the rail was promised to be $33B and be completed in 2020. By 2018 it was over $100B and estimated to be completed in 2033 -- so is estimated to take 2.5 times as long to complete and 3x the original costs -- that is if you're gullible enough to believe that the current estimates won't get revised again.
What you could build instead: 
High speed rail would be great for me: it's stealing billions of dollars from the poorer parts of the state and nation, to subsidize a rail line that will be under-utilized, but convenient for a few. And I'm one of the few. That being said, since I'm not greedy/selfish or as misinformed as the supporters, I think it would be better if this thing died a quick death (and better still, if the math challenged had realized how flawed the boondoggle was from the get-go). Planes and busses will be cheaper, faster and more economical, and the world doesn't need another testament to Jerry's ego, and the gullibility of California voters.
Yup. The difference between investment and public works, is in the former you have to convince investors to choose to support something risky, because of the potential returns (either to society, or economically). In the latter, you just force people to invest, even if they completely disagree with the risks/returns (like California's crazy train). 51% of the most gullible, in two cities (LA and Bay Area) get to force the rest of the state to fund their loser boondoggle, that few private investors would take a chance on. In the meantime real investment in the future is going on elsewhere, by private concerns. Texas and Florida's high speed rail is progressing based on actual private investment. We'll see which gets built first, and still exists in 100 years: California's 19th century network between Bakersfield and Fresno, or one of the others between two closer metros, and that can actually compete with air-travel in speed and cost.
Not that high speed, but still... Turns out Texas and Florida are doing theirs private, California is doing their high speed rail by politician... Want to take bets which will get done faster, for less, and carry more passengers per population? At least ours has a better theme song...