If you don't think Bitcoin is safe, don't invest anything into it.  That limit is unchangable, though, not because of the code, but because of the principle.  If there were to ever be a hard code fork on this issue, one would be the true Bitcoin, the other could not be.  It's also more than a bit rediculous to assume that future users would be running a full node, and could be tricked into supporting such a change simply by turning on an auto update feature.  First off, the vast majority of future bitcoin users, if bitcoin is ever truely succesful, will be running light clients or depending upon wallet service accounts; the full client will be the realtively rare animal.  Probably as many or more full nodes as presently exist, but still realtively rare overall.  Second, a group of end users, both stupid enough to trust their internal security with their money to a remotely controlled automated system AND wealthy enough to ignore the ongoing costs of running a full node would still amount to little, IMHO simply because there are now, and shall be, more than just the main reference client.  So whatever percentage is deceived into supporting the change will still be opposed (by default) by those nodes that do not authorize or otherwise cannot participate in an auto update.  Furthermore, the break wouldn't go unnoticed for very long, and a great many of the decieved users can and will revert.  The 21M limit is part of what makes Bitcoin what it is, if you don't like it or don't think it's going to work out, you can either support one of the alt-coins that suits your needs or start your own.  Just don't call it Bitcoin.