What happened

Shares of Wayfair (NYSE:W) continued their massive run higher on Monday, adding another nearly 6% to their gains as of 4:15 p.m. EDT, even though Stifel analysts downgraded the stock because it had exceeded their price target.

So what

The online retailer has been on a tear since mid-March, surging 500% over five weeks, as it has benefited from a deep bench of available products and quick turnaround time on delivery.

Movers delivering furniture.

Image source: Getty Images.

It suggests it is benefiting at least in part because rival Amazon.com (NASDAQ:AMZN) has prioritized fast shipping only for essential goods while putting all other products in a queue that could delay their delivery for weeks at a time.

Yet Morningstar analysts also see potential problems on the horizon as competitors won't stand still. Analyst Jaime Katz wrote in a note, "Wayfair is competing with mass-market retailers, specialty retail, and low-cost providers, making it harder to stay front of mind perpetually."

Now what

With consumers stuck at home and forced to shop for non-essential goods online as physical stores remain closed, Wayfair ought to continue to gain, though the run-up it's experienced could very well reverse in short order.

States are beginning to allow retailers to open their doors again, which could increase the competitive pressures analysts foresee. Moreover, massive rates of unemployment could impact the consumer's ability to keep spending on big ticket items.

Investors may see some good results when Wayfair reports earnings next week, but the outlook is murkier further out.