I believe I fixed this earlier this week - please make sure you are using v0.95060 and not 0.95059 ... use shift-reload etc. Please report if the issues are still occurring - I have tested various combinations of IE, FF, Chrome, Safari & Win7, WinXP, OSX, IOS and not seen issues now with hitting "Go". The issue I fixed was due to a change in the way that Javascript was handling "undefined", and wasn't related to AddThis etc.
I have no objections to removing the AddThis functionality - address bar links are the most common usage - and these are available without addThis. From functionality AddThis provides, over the last year there have been 10 shares to FB, 6 to Gmail, 4 to Print, and then "Others" such as StumbleUpon adding up to 12. Based on this, it seems there's no real need to keep it around - especially if it's implicated in issues. Let me know if anyone really wants to keep it, else I will plan to get rid of it.
In other areas of disclosure, the Google ads help offset some of the costs I incur (e.g. server hosting - US$77/pa; one server is kindly hosted for free by an AFFer), and since putting the ads in (May 2011), Google have paid me US$138 - so by no means is it a money spinner for me as on a strictly financial basis MM is making a loss! Don't feel bad if you have AdBlock hiding the ads ... I do too! Maybe I should add a Donate button and remove the ads?
MM gets about 100 page hits per day - as reported by StatCounter (I assume that SC will be blocked by some filters, so the true page hits will be higher). I'm not particularly interested in the stats/analytics, however it does reassure me that the site is being used and that I should keep investing time in it. Additionally, it's nice to see that approximately half the page loads for MM come from Australia (USA is second at about 18%).