Depends on the line of work.

Retail is pretty mindless stuff, so I don't see anything wrong with going to work high in that context. Provided, of course, you don't get too baked. Years ago when I was in retail I would go to work high pretty often. When you're on your feet, jumping between registers, helping customers, and answering the phones it's pretty easy to remain sharp since the work is more physical and social. I worked for a reputable, high end clothing retailer on one of the larger shopping districts in the world, and almost everyone openly smoked. I think it's the only way anyone can handle working in that environment for such shitty pay. I know my attitude was always better when I went in high.

I've moved on professionally since then, and now I'm an accountant. My current job just involves too many new day to day challenges to handle while high. Admittedly I tried it a few times. Discussing the finer points of taxing complex non-profit partnership structures with the CFO proved to be a little overwhelming. Company policy states I could also face termination if anyone found out I was high on the job. So, now I just wait 'till night time. Keeps the tolerance lower I suppose.