It doesn't make you explode or anything, it just shows you on the radar.
They still have to catch you, fight you, kill you, and grab it... You can still evade enemies once it is on - however, we had known since day one that the game could be brought to a halt by a player simply finding a hiding spot and riding out the clock (because they fear losing, or just because they're a jerk)... We hoped that in practice it was difficult to hide and in extreme cases, voting would be an option, but we'd always wanted to find time to fix it in a more general manner - so we did.
Evading is a valid tactic if you're trying to avoid losing an artifact or need to buy time for energy, but in such a situation you should rely on your teammates for protection or your own skill to save you - two minutes is a long time.
If you're simply trying to be a jerk and exploit a hiding spot you've found in the map to ruin the game for everyone, well, the idea of you moving and having the support of your team probably don't apply.
This works well in practice, and it tends to encourage teamplay if you're in a tight spot waiting for energy or defending the last artifact. It adds to the tension when you're playing legitimately, as well as removes the exploit that ruins everyone's fun.
The time limit is of course configurable on the server, but we found two minutes was a good amount of time in usual gameplay situations...