Joop Dorresteijn, a contributing editor at The Next Web, has found a painfully easy way of artificially inflating the feed count of a blogs FeedBurner chicklet. Basically, all you need to do is create an OPML file with the same feed copied and pasted as many times as you want and then import this into your NetVibes account.
This video explains how it works :
Feedburner hacked! from Boris Veldhuijzen van Zanten on Vimeo.
I applaud Joop for exposing this hack and I hope that FeedBurner fixes this soon. Personally, I wouldn’t advise anyone to use this hack. Inflating your subscriber count may sound like a good idea just now but when they fix this hole in their system your feedcount will reduce back down to it’s true level and you’ll look a bit silly to say the least.
Call me cynical but I believe there will be many bloggers out there who will use this hack. Expect to see many blogs get an unexplainable surge in subscribers over the next week or so followed by a sharp decline once the flaw gets resolved and an apology to readers for doing it in the first place! 
Link : Feedburner hack: how to get 2500 subscribers overnight
Yah…. I think Shannon Lilly over at infectedbybugs.com increased his count artificially…. he was hacked, and his subscribers went down, then when he came back, his count was down, and rose over 150 in like 5 days, at almost a rate of 30 a day… when previously he had not been gaining at nearly anywhere close to that amount…. and, it all started rising when he was trying to sell his blog at sitepoint and wasnt getting the amount he wanted for it… and his subscriber amount keeps rising and rising.
his subscriber amount keeps rising and rising.
Well, you can expect a lot of people to use this hack. As for Feedburner fixing the problem, I believe it’ll take some time or they’ll completely ignore it.
You would think that once they identified this hole, they would close it. If not I'm siging up for a netvibes account now and see what happens.