7D is not entirely "weather sealed". It had improved seals for better "weather/dust resistance" than the xxD models, and equal to or a step up from the 5DII. I don't think any camera with a built in, pop up flash can be all that thoroughly sealed, but Canon claims it's as well sealed as the 5DII, which doesn't have a built in flash.
Even the 1D series aren't completely weather sealed. A few years ago at a rainy super bowl Canon went through all their loaner cameras because the pro shooters they were there to support were killing off their cameras left and right. The reason was when switching out memory cards water was getting inside the compartment and shorting out the cameras.
I've been caught in a downpour with a pair of 30D (w/lenses and 550EX mounted), turned everything off and removed the batteries and memory cards (being careful not to get any more water inside), dried things out throroughly over a couple days and everything still works fine today.
"Weather resistance" adds seals around buttons and dials, gaskets on doors and where the camera's external body panels fit together. It's not a complete seal, but will keep out a lot of dust and most moisture.... There just aren't any guarantees.
It's similar to the shutter rating. Canon claims to have tested it and found a mean failure time of 150K... But that isn't a guarantee, either. It might fail with 10K clicks or 210K clicks. Either way if it's in warranty it will probably be replaced. (They might argue excessive use if a 10 month old camera has 210K clicks on it.)
Don't fret too much about the memory cards, either. Just avoid fakes that are lower quality cards marked as if they are higher speed. Over the years I've used Lexar, Sandisk, Sony and Kodak (which were Lexar) compact flash without any problems.
I currently use twelve or fourteen 8GB cards with 7D and 5DII, about half Lexar 300X UDMA and half Sandisk 60MB/sec UDMA. I bet the Transcend are about equal and am looking at some Transcend cards myself to give them a try. I'll stick with using 8GB in 7D, since they give me a bit over 200 RAW files apiece. I try not to put all my eggs in one basket with too large cards. I'd like to have a few larger cards to use with 5DII, in particular.
B&H Photo and Amazon both have Transcend 400X UDMA 16GB CF for about $60. The Newegg price looks good, but if they are sold out...
I bet a lot of memory cards are actually made by just two or three or four manufacturers, then relabeled with different brand names. For example, I know that at one time Kodak cards were actually made by Lexar. Don't know if they still are.
All compact flash cards themselves are reasonably "weather resistant", by design. The solid state memory chips are encapsulated within plastic, which pretty well seals it up. I've heard of some going through the laundry in someone's pocket and coming out fine... But I sure wouldn't recommend that.
The weak point of Compact Flash are the pins and sockets. Occasionally pins in the camera get bent or even broken off inside the card's socket. Not all the pins are actually used, so sometimes this doesn't matter. But more often than not it is a problem. Knock on wood... I've never had a problem with CF pins on any camera, and sometimes I do a dozen or more swaps during a shooting day. I'm careful to insert the card squarely and never force it. I have an Expresscard memory reader for my laptop that's a little fussy fitting a card in... But that's just the design of the reader. (On the other hand, it's damned fast.... 54MP/sec.)
