This was directly from an entry level offer and it is general practice to get a salary increase at annual reviews and more RSUs for after your fourth.
Like many RSUs, if you leave before your RSUs vest, you forfeit them. This is pretty much your 4 year incentive to stay.
EDIT: Clarifying RSU forfeiture
As for signing bonuses, I have read contracts from various startups that want you to pay your signing bonus (which is generally about 5k) back if you leave within the first year.
I have heard stories from other employees, claiming that entire teams were fired, and workloads were transferred to the remaining employees - however they have been just that - unverified rumors.
I totally agree, I don't really like it. I think, though, that the astronomically large bonuses are worse than the small ones. Paying back $5000 (+ income tax, mind you) is much easier than paying back $100k + tax.
RSUs are back loaded. I forget the exact numbers, but it is something akin to 5% vested after 1st year, then 15%, then 35%, so after 2 years the vesting schedule makes it pretty hard to walk away from, especially with the current stock price. "If I stay just another 3 months I get 45 thousand bucks over my salary... hmm...."