To me the worst offender is not loss of data (seriously this is just a web form) but loss of context. Having the current location change is disorienting to the user† especially when it's not the expected result.

IIRC Safari had some CMD+Backspace ("Clear history") that I kept on triggering the same way, as in a Cocoa text field it means "Clear from cursor to beginning of line"), but apparently they (thankfully) removed it too. The process, and resulting effect, was the same.

Basically in terms of usability this boils down to the key behaviour following an implicit mode (triggered by what's focused), making it hard to discover (or discovered the hard way) and unpredictable.

This is similar to Safari's braindead CMD+Z that does both "undo in a text{field,area}" and "reopen last tab".

† even though I myself know what happens I am taken aback every single time because it just breaks the flow, resulting in grievous annoyance. Therefore, props to the Chrome team.