Mass. Rule 4: http://www.lawlib.state.ma.us/mrcp4.html Federal Rule 4: http://www.law.cornell.edu/rules/frcp/Rule4.htm
Did you receive a summons or was it just a printout of what we saw in the TC article? Insufficient service is grounds for dismissal. The plaintiff has time to correct, though.
You should see if there are any users in Delaware. If not, I doubt you can be compelled to court there. Even if you do have users in Delaware, it is a stretch.
For everyone on YC News, this is a reason to incorporate in your home state, not Delaware. Incorporate in Delaware if you want VC funding. Otherwise, stay in your home state. If you incorporate in Delaware, or any other state for that matter, courts automatically grant personal jurisdiction in that state. Basically, that means you have to go to court there.
This is also a reason to incorporate. Right now shimon is personally liable for damages, if any.