Overclocking with locked multiplier?

Why is it that people used to always overclock with locked multipliers (like the first series i5s), but now people say it is  a "no-no" unless you have one of these unlocked "k" chips? Couldn't you overclock by changing the bclk in bios with any modern-day cpus?

Because that main bus (base clock) is also tied to other components that don't like being changed. I think the PCI bus is tied the base clock now.

You can overclock without the multiplier it just becomes  a pain in the ass to troubleshoot. For me, my sound "hangs up" or I start losing USB connection at around 105 bclck if I push it too hot. RAM speeds increase as well, which was my original intent with messing around with bclcks, but you better have some patience.