Warning: contains spoilers for Amazing Spider-Man #87!
Marvel's Spider-Man has officially lost his mask and has substituted the classic Spidey visage with one of the lamest disguises ever for a superhero - but oddly appropriate for Spider-Man. Peter Parker's been through the wringer as of late, surviving a deadly attack that nearly resulted in his death. Now in Amazing Spider-Man #87, the webslinger is forced to become the Amazing Bag-Over-Head-Man to conceal his identity...even though there's a good chance it's already blown.
Spider-Man has just suffered a deadly radiation-based attack from the U-Foes and landed in the hospital for quite awhile. The attack severely weakened Peter, and while he recuperated, Ben Reilly (Peter's perfect clone) took over Spider-Man duties while employed at the Beyond Corporation. Now that Peter feels well enough to regain his Spider-Man title, he meets up with Captain America and ex Black Cat (Felicia Hardy) for an impromptu training session - but Black Cat snatches away Spider-Man's mask and suit ("Because right now, you're not Spider-Man" explains Hardy).
Peter Parker is quite weak and woefully inexperienced at swinging through the city, but he still needs a training session or two if he wants to keep up with his fellow superheroes (let alone his villains). As such, he swings into action alongside Black Cat in his street clothes - and since Hardy still keeps the mask, Peter has resorted to placing a paper bag over his head to conceal his identity. It barely works - Peter even crashes into a table while swinging low - but it at least hides his face from the general public. Unfortunately, his clone may have blown both of their identities at once.
During Marvel's Devil's Reign event, Ben Reilly was captured and interrogated by the NYPD. The police have unmasked him and have seen his face, but they are unable to take his fingerprints due to other, more Spider-Man-sympathetic officers in the department who view the wallcrawler as a hero. Since Ben is Peter's perfect clone, the interrogating officers can easily pick Peter out of a crowd and figure out his identity as Spider-Man.
Spider-Man's bag-over-head disguise is the latest in a line of improvised disguises used by Peter. He's covered his face with webbing on more than one occasion, and has even used various Halloween masks when his regular mask was unavailable. Spider-Man's disguise might be incredibly lame, but aesthetics aside, it still serves to hide his most important secret: his secret identity.