I am a long time RPG player, but new to Shadowrun. I believe that gives me perhaps a different perspective than some others, as I don't have preconceived notions of what the rules should be - I am only reading what they are.
I have read through all 7 pages of this, and I think as a new player, reading only the 4th edition rulebooks, I would be confused by the interpretation of MBW inflicting TLE-x, by default.
If you're inflicting TLE-x on your players (a consequence with game mechanics behind it) for taking MBW, do you inflict it on them for taking Wired Reflexes and Skillwire? Do you inflict it on them for other Cyberware? What is your threshold? The wording quoted numerous times above doesn't actually give rules for deciding this, just an indication it is a possibility (fluff), and if you choose to go this route as GM, some guidelines on how you might work it.
Again, as a new player, I don't see the rules that say this must happen, so for me it falls directly in the "GM decides how his world works" realm of territory. So, from my perspective, if you are inflicting TLE-x on players in your game for taking MBW, that is totally up to you, but the base rules don't support it. As a player, I would be against this ruling, as it seems rather arbitrary in relation to the other mechanical options available (by mechanical I mean in terms of game mechanics; IE - Not Fluff).
My final comment is simply to echo what others have said before and I think all agree on - Communication is key. If this were to just suddenly happen to my character, and I as a player had no idea it was a possibility, I think I would have a right to be little miffed. If the GM tells me upfront that MBW definitely causes TLE-x, I would be against the ruling, but I could choose to just Wired Reflexes + Skillwire + Reaction Enhancers instead, if I really wanted to avoid it. If the GM tells me that being all Cybered up also has the chance to cause TLE-x, in addition to MBW definitely causes TLE-x, I would wonder what the GM has against Cybered characters, and choose between playing a non-cybered character (Mage? Technomancer? Adept?), playing a character below the GM's pseduo "cyber limit", or not playing at all. In any case, knowing beforehand is crucial to making informed decisions about how we choose to play this game, which should ultimately be fun for everyone involved, players and GM alike.