Maybe you should have checked that for yourself before requesting it?
IE7 64-bit, 50 tabs all open to this page = 329MB at first, jumped to around 750MB when all the flash ads loaded.
FireFox 3 beta 5, 50 tabs open to this page = 221MB.
Still..... nowhere remotely even close to 5 times the usage.... which would be around 1105MB. Guess i should also mention that IE7 has a bit lower CPU usage when doing nothing.
Seems to have a bit of an issue freeing up memory from tabs that have been closed though. going from 50 tabs down to only one, IE7 is using 337MB, while FireFox is only using 81MB. still not 5 times..... but either way, with one tab, closing IE and opening it again starts out with a fresh, low number.
Now.... if you were talking about basically 49 blank tabs, and one tab opened up to a webpage (as another example... this one).....
IE7 64-bit = 58MB
FF5 beta 3 = 42MB
Sooooo.......... yeah...... how is it such a memory hog? Yeah.... at 50 in-use tabs, it's using 750MB, even though on a webpage with no ads it would probably still sit around that 329MB mark.... maybe slightly higher, maybe slightly lower depending on exactly how much is on that page, but seriously..... has ANYONE actually USED even 15-20 tabs at the same time? highly unlikely, and if so, extremely rarely. If you do so on a regular basis.... you've got some issues.