Because ObjectId needs to get the current time, it panics in wasm, which can't get the current time via std (see: https://github.com/rust-lang/rust/issues/48564).

Issue originally filed by sinhpham on GitHub (https://github.com/mongodb/bson-rust/issues/199):

Due to using std::time::SystemTime.

A potential solution is exposing a new_with_timestamp(n_secs_since_unix_epoch: u32) -> Self constructor. People who want to run on wasm can supply their own timestamp.