I've seen plenty of burned standard receptacles thought the years. However, rarely do those melt and disfigure. Generally, it's on older plugs that have worn out and gotten loose and no longer make solid connections. A standard edison plug in good working order can handle a 20 amp load with no problem.
Power strips on the other hand, I've seen a ton of that end up melty and completely disfigured, even on relatively new units. The material is SO cheap that even brand new if you try and draw 15 amps from a single outlet on the strip, chances are it'll get hot. The connections inside are often built so poorly that just a few insertions cause them to get loose, and the problem quickly gets worse.
For low current draw loads like phone chargers and whatnot, they're fine. Anything that's drawing more than 5 amps, I don't like using power strip outlets.
