checking your rankings regularly (many times in a day) with an automted tool mite cause google to ban you IP for sometime but i mite not affect your SEO..

nope, because (in the case of market sam and most of the time) you're not actually visiting any of the websites so how could it link a particular search to a particular website?

You should always check SEEPs via private browsing whilst not signed into a Google account. If you don't the results will be personalized and based on your search & browsing patterns.

If you want to test this out try a term your trying to rank for and see if G personalizes your target site higher when in non-private mode. You'd be surprised how often they do.

Checking your PR regularly, many times a day will drive you nuts. Google only updates PR about quarterly, so if it is PR3 this morning, the chances it will change during the day are pretty slim, less than 1 in 90, even if you were to get a change every time they did it, it would only be one time out of ninety.

I do not think it will change your rankings, but what it may do is eventually skew the stats in the Google Keyword tool for low volume search terms.

eg: If I check my rankings for purple vibrating banana toy 10 times a day for 90 days from a range of IP addresses, I believe purple vibrating banana toy will end up as a listing in the Google Keywords tool.

You'll learn eventually that you can have more productive time than checking your ranking every 5 minutes. Get your head down and get on with some productive work! (I know it's tempting though - been there, done that!)

Off the topic, but it helped me clear few points i had in my mind.
Thanks

It might negatively effect your personal experience as Google user but not rankings of your site.

Personal Theory: The only exception would be if your personal computer is also server of your website.

If you wanna be certain use Chrome Incognito or it's variation in other browsers or VPN to check your rankings.