A few thoughts that came to me while perusing the thread.
1) So what about Harry's van? Image: http://s9.postimage.org/ksg2xlf0d/vlcsnap_2012_05_20_18h20m47s218.jpg
Where'd he get the van? Harry is a low-level crook. Are we supposed to believe that bought the van? Not likely. It's probably stolen. Yet, he's just creeping around a neighborhood and parking in peoples driveways? Okay let's say it was Harry's own van. So he decided to have a big logo painted on the side? Ha. And should we believe that Harry was gainfully employed by Oh-Kay plumbing and heating? Even if he were, he likely wouldn't have control of a company van after dark. Yet he pulls up near 9 pm driving the van?
2) Harry and Marv are prison escapees. They got out of prison in Chicago during a prison riot. So fresh out of jail, they managed to fund a trip to New York? Then, as escaped felons, they're just wandering the streets of the biggest city in the United States? You'd think they might lay low or change their look. But here they are walking the sidewalks of New York looking the exact same as they did in Chicago.
3) How about the mess that would have been in the house? After Kevin's big adventure I doubt he had the energy to clean it up before his family got home the next morning. Obviously he didn't clean up Buzz's room (which wasn't even related to the big plan). Let's look at the messes that would have been left behind.
~Between night and morning when the family got home, the ice likely wouldn't have melted off of the stairs.
~The blowtorch is attached to the back door (which gives me another point I'll address later.)
~There is feathers all over the dining room floor
~Broken ornaments around the Christmas tree.
~Paint cans and a big arse pipe hanging from the stairs
So Kevin has a huge fricking mess all over the house and that's not the first thing the whole family sees when they walk in. Also he's lucky nobody came in the back door. And don't get me started on HA2 when Kevin broke into his relatives house and made a huge mess of their remodel.
4) Image: http://www.google.com/url?source=imglanding&ct=img&q=http://4.bp.blogspot.com/_dO5wi4i0JDs/TRI_zFSkR1I/AAAAAAAAAlI/VhQMwWMO8ss/s1600/harry1.jpg&sa=X&ei=rLbCUMyOCI-o9gSsxYCIDg&ved=0CAkQ8wc&usg=AFQjCNGllYYVXceEaPEtMV0q8fH_-BQURg
The fricking drapes are on fire! Given how much material is there, that fire would have spread fast and likely burned the house down.
5) The McCallister's have 5 kids. Surely they're friends with parents of other kids. Ok the neighbors are out of town? Surely you've got some friends that stayed in town for Christmas who could go over and check on Kevin. And don't give me the line about the phones being out because Kevin ordered a plain cheese pizza.
4) The polka band guys are trying to get back to Chicago and the best vehicle they can come up with is a Budget Rental box truck? I'm sorry, I didn't realize that Christmas time means a run on 15 passenger vans.