Spider-Man is arguably one of the most well known/popular Marvel superheroes/superheroes in general. Many people who do not read the comics at all got introduced to not only Spidey, but the entire Marvel Universe through his cartoons (especially the 1994 Animated Series). Marvel's The Avengers was the top grossing movie of 2012. Even people that did NOT see the other films leading upt to it loved it! Many Marvel fans want to see ALL the characters come together, which other people would love too, as Spider-Man is something that many people would know, which would draw even more people to the box office for the Avengers/other Cinematic Movie sequels. As well, there are many reasons why ASM(Amazing Spider-Man) should cross over with the MCU(Marvel Cinematic Universe):
1) As per this video,http://www.youtube.com/watch?v=sPQ9YW_ogEU, S.H.I.E.L.D. would tie in well with the ASM world and Story. Peter's parents worked for S.H.I.E.L.D. in the comic books/1994 cartoon, and their reaserch on the cross species would fit really well into the MCU with all thats been going on. They already have similar tones, and Nick Fury could easily show up and tell Peter the truth behind his parents.
2) Mark Webb's quote with regards to building a Spider-Man universe with the sequels was "Think Bigger". He's also said that he would love to crossover with the new Fantastic Four movie which already has contitnutity with the X-Men movies; its also been hinted that there will be more heroes in the ASM2 and ASM4 could be a "spin-off" film
3) The Oscorp Tower from the ASM was originally going to show up in The Avengers, but had to be scrapped when its designs were incomplete on time with the rendering of The Avengers' skyline.
4) in the Iron Man 3 Video Game trailer, the Oscorp logo from the ASM movies shows up in a city level. Correct me if I am wrong, but does it show up in the final game?
5) Andrew Garfield has repeadetly stated that he would love to show up in the Avengers sequels. Avi Arad has also stated that the idea is possible.
6) Disney already owns all merchandise (excluing the video games/mega bloks sets) of the ASM, and since they already own everything else Marvel (excluding the X-Men/Fantastic Four/old versions of Marvel movies), why not include ASM in the MCU?
7) According to polls here: http://marvelcinematicuniverse.wikia.com/wiki/User_blog:Greater_good/Should_The_Amazing_Spider-Man_be_tied_into_the_Marvel_Cinematic_Universe%3F_(updated_with_poll)
many poeple would LOVE to have ASM cross over
8) Vin Disel has recently hinted at a "merging of the brands" for MCU Phase 3
9) If Spidey does show up without the ASM, then they will have to reboot Spidey again, which is something many people criticized about ASM in the first place in showing the origin and many people do NOT want there to be a third reboot!
Please, give it a chance! If enough people sign this, then Disney/Marvel could pull strings together to make this happen